Imaan(Faith) is to accept with the heart all those things which are the necessities of Deen. To reject any one of the necessities of Deen is known as Kufr (infidelity), even if one accepts all the other necessities of Deen. Necessities of Deen refer to all that which ever individual Muslim is aware off. In other words, the Oneness of Allah, The Nabuiwat of Prophets, Jannat, Jahanum, Resurrection and Reckoning etc. For example, he must accept the finality of the Holy Prophet (sallal laahu alaihi wasallam). This must be accepted without any doubt or reservations. Any Muslim who does accept these principles of faith is no longer a Muslim. A Muslim who lives in a normal community have to be aware of the fundamental necessities of Islam. This however does not apply to those who live in mountains and forests etc. which is completely away from civilisation. This category of people will not lose their faith if they are unaware of these aspects of faith. These people will be regarded to be out of the folds of Islam if they totally reject any basic Islamic beliefs. The above mentioned law is only for those who are away from actual civilisation. This law will not apply to those of us that live in civilised communities and are aware of all the necessities of Deen. Such Muslims who live in civilised societies need to also follow the commands strictly through their practices and statements.
It must be noted that this refers to communities that are totally distant from civilsation, meaning that none from another community is able to go them and none from their community is able to go to another place to attain proper knowledge of Deen.
Belief: The sincere conviction from the dept of the heart is the actuality of Imaan. The physical actions are not part and parcel of Imaan in actuality. As for the announcement of Imaan through word of mouth, then if after accepting Islam, a person does not get time to say this with the tongue, then in the sight of Allah he is a believer. If he had the time to say it with the tongue and he was asked to do so and he still abstained from doing so, then he is still a Kaafir. If he was not asked to confirm his Imaan verbally or secretively, then according to the law in this world he will be recognised as a Kaafir. Neither will his Janaaza Namaaz be performed and nor will he be buried in the Muslim cemetery, but in the sight of Allah he is a Muslim (as Allah is aware of him secretly accepting Islam in his heart), for as long as he does not portray any action which is against Islam.
Belief: To be a Muslim, it is also compulsory not to verbally reject anything which is from amongst the necessities of Deen. Even if a person accepts all the other necessities and says that he is only rejecting it verbally but has faith in it in his heart. A Muslim can never utter words of kufr and only he will utter such words of kufr, who harbors such thoughts in his heart, and says whatever he pleases whenever he pleases. Imaan is such a firm conviction, that there is no room for disagreement present in it.
Mas'ala (Rule): If (Allah forbid) a person was forced into uttering words of kufr, in other words, his life has been threatened and those threatening him say that they will cut off his body parts etc. then one must be completely sure that the ones threatening definitely have the ability to do this, then in this circumstance, he is given latitude. However, in heart he should still have conviction of Imaan and it should actually be even stronger now. It is however more exalted that one gets killed and does not utter these words of kufr.
Mas'ala (Rule): Ones physical practices are not included in the actual theory of Imaan. There are however certain actions which when done, will cause a person to become a kaafir. Examples of these actions are : To make sajdah to the sun and the moon, to kill a Prophet, to say blasphemy against a Prophet, To insult the Kaaba Shareef or the Holy Quran, or to look at any sunnat with in a bad way. All these are without doubt Kufr. In the same way, there are certain practices which are signs of kufr, such as wearing a Zannaar, growing a choti (bunch of hair grown on the back of head by hindus), or applying the qashqa (the mark made on the foreheads by hindus indicating their conviction as hindus). The Great Jurists have labelled one who does these actions as a Kaafir. Now, that these actions show kufr, then the person who has done them will have to read the Kalima again and make Nikah again with his wife if he was married.
Mas'ala (Rule): To say that to be haraam, which is prove to be halaal from the Quran and to say something which is ordained as haraam to be halaal is Kufr, on condition that this command is from the necessities of Deen and the one who is rejecting it is well aware of the command.
Mas'ala (Rule): In the principle beliefs (Usool‑e‑Aqaaid), one is not allowed to make Taqleed (To have difference of opinion like the four Imams have on issues of practice such as Namaaz, Fasting etc). To make taqleed in certain practical aspects of Deen is allowed. It is for this reason that there are two basic branches in the Ahle Sunnat. One is the "Maatureediya" in other words those that prescribe to the school of thought of Hazrat Abu Mansoor� Maatureedi (radi Allahu anhu) and "Ash'a'ira, who prescribe to the school of though of Hazrat Imam Sheikh Abul Hassan Ash'ari (radi Allahu anhu). Both these branches are proper branches of the Ahle Sunnat Wa Jamaat. Both are on Haq (The True Path). They do not differ in principle beliefs Belief. Their differences are in certain practical issues (such as Namaaz, wudhu etc and how these practices should be performed). Their differences are like that of Hanafi and Shafi'i etc. Both are on righteousness and one can not contradict one another.
Mas'ala (Rule): There is no increasing or lessening in Imaan. Only that which has form, shape, height, width and length can be increased or lessened and Imaan is pure of all these. Imaan is declaration and a declaration is a condition of submission. In certain verses of the Quran Allah azzawajal has mentioned enhanced Imaan. This refers to faith with true conviction in Imaan (It does not mean that the value of Imaan is more. It however does signify the strength of Imaan). In the time of the revelation of the Quran, there was no limit fixed for this. As the verses of the Quran were revealed, people brought Imaan on them the commands which were revealed. It is not such that the reality of Imaan increased or decreased. However, there is difference in the strength and weakness of Imaan of every individual (in other words the Imaan of some is stronger or weaker than that of others, meaning one has stronger or weaker faith than another). For example, the Imaan of Hazrat Abu Bakr Siddique (radi Allahu anhu) is stronger than the Imaan of the rest of the Ummats Imaan all put together.
Belief: There is no relationship between belief and unbelief. A person will either be a Muslim or a Kaafir. There is no third thing, that a person is neither a Muslim nor a Kaafir.
Mas'ala (Rule): Nifaaq (Hypocrisy), in other words to make the verbal claim of Imaan yet reject it in the heart is also kufr. The lowest level of Jahanum has been prepared for such people. There were also those in the time of the Prophet (sallal laahu alaihi wasallam) who were hypocrites. These hypocrites were exposed through verses of the Holy Quran and the Prophet (sallal laahu alaihi wasallam) with his vast knowledge recognised every one of them and said each one of them to be Munafiqs (hypocrites). Today, we can not call a person a Munafiq if he announces Islam and does not openly go against any principle beliefs, as we are not aware of his hearts condition. However, there are those misguided sects today who claim to be Muslims but reject the necessities of Deen as well.
Belief: Shirk means to make any than Allah worthy of worship and to accept more than one Allah being in existence. This is the worst form of kufr that one can commit. With the exception of this, any other Kufr, no matter how bad will not amount to Shirk. The command in the Quran that no shirk will be forgiven refers to all types of shirk and kufr. However, Allah azzawajal may forgive any other sins that he wills too (This is except kufr and shirk).�
Belief: One who commits major sin is still a Muslim and he will not be deprived of Jannat. This will be through the Grace of Allah and the intercession of the Holy Prophet (sallal laahu alaihi wasallam), or after getting some punishment for some of his deeds.
Mas'ala (Rule): Any person who makes dua for a kaafir after his death, or refers to a dead murtad (one who turns away from Islam) as 'Marhoom' or 'Maghfoor' or addresses a dead hindu as a heavenly soul is a kaafir.
Belief: To call a Muslim a Muslim and a Kaafir a Kaafir is from the necessities of Deen. To doubt the Kufr of any person who openly made kufr also causes one to become a kaafir. The law of Shariah is passed on that which is apparent and not that which is not known, for example if a Jew dies, then we will regard him as kaafir and will treat him as he should be treated after his death (not make dua for him etc.). If a Muslim dies and he did not openly reject any necessities of Deen, then we will treat him as a Muslim even after his death. There are those who say that we in the time we spend calling someone a kaafir, we should rather chant the name of Allah. Let us inform them that where have they seen us continuously chanting the words Kaafir, Kaafir. What we are saying, is that a kaafir must be called a Kaafir and a Muslim must be called a Muslim. They should not use their Sulah Qul (Compromising) tactics to put a veil over the kufr of any person.
source: http://www.islamieducation.com/en/islamic-faith/faith-iman-and-unfaith-kufr.html
It must be noted that this refers to communities that are totally distant from civilsation, meaning that none from another community is able to go them and none from their community is able to go to another place to attain proper knowledge of Deen.
Belief: The sincere conviction from the dept of the heart is the actuality of Imaan. The physical actions are not part and parcel of Imaan in actuality. As for the announcement of Imaan through word of mouth, then if after accepting Islam, a person does not get time to say this with the tongue, then in the sight of Allah he is a believer. If he had the time to say it with the tongue and he was asked to do so and he still abstained from doing so, then he is still a Kaafir. If he was not asked to confirm his Imaan verbally or secretively, then according to the law in this world he will be recognised as a Kaafir. Neither will his Janaaza Namaaz be performed and nor will he be buried in the Muslim cemetery, but in the sight of Allah he is a Muslim (as Allah is aware of him secretly accepting Islam in his heart), for as long as he does not portray any action which is against Islam.
Belief: To be a Muslim, it is also compulsory not to verbally reject anything which is from amongst the necessities of Deen. Even if a person accepts all the other necessities and says that he is only rejecting it verbally but has faith in it in his heart. A Muslim can never utter words of kufr and only he will utter such words of kufr, who harbors such thoughts in his heart, and says whatever he pleases whenever he pleases. Imaan is such a firm conviction, that there is no room for disagreement present in it.
Mas'ala (Rule): If (Allah forbid) a person was forced into uttering words of kufr, in other words, his life has been threatened and those threatening him say that they will cut off his body parts etc. then one must be completely sure that the ones threatening definitely have the ability to do this, then in this circumstance, he is given latitude. However, in heart he should still have conviction of Imaan and it should actually be even stronger now. It is however more exalted that one gets killed and does not utter these words of kufr.
Mas'ala (Rule): Ones physical practices are not included in the actual theory of Imaan. There are however certain actions which when done, will cause a person to become a kaafir. Examples of these actions are : To make sajdah to the sun and the moon, to kill a Prophet, to say blasphemy against a Prophet, To insult the Kaaba Shareef or the Holy Quran, or to look at any sunnat with in a bad way. All these are without doubt Kufr. In the same way, there are certain practices which are signs of kufr, such as wearing a Zannaar, growing a choti (bunch of hair grown on the back of head by hindus), or applying the qashqa (the mark made on the foreheads by hindus indicating their conviction as hindus). The Great Jurists have labelled one who does these actions as a Kaafir. Now, that these actions show kufr, then the person who has done them will have to read the Kalima again and make Nikah again with his wife if he was married.
Mas'ala (Rule): To say that to be haraam, which is prove to be halaal from the Quran and to say something which is ordained as haraam to be halaal is Kufr, on condition that this command is from the necessities of Deen and the one who is rejecting it is well aware of the command.
Mas'ala (Rule): In the principle beliefs (Usool‑e‑Aqaaid), one is not allowed to make Taqleed (To have difference of opinion like the four Imams have on issues of practice such as Namaaz, Fasting etc). To make taqleed in certain practical aspects of Deen is allowed. It is for this reason that there are two basic branches in the Ahle Sunnat. One is the "Maatureediya" in other words those that prescribe to the school of thought of Hazrat Abu Mansoor� Maatureedi (radi Allahu anhu) and "Ash'a'ira, who prescribe to the school of though of Hazrat Imam Sheikh Abul Hassan Ash'ari (radi Allahu anhu). Both these branches are proper branches of the Ahle Sunnat Wa Jamaat. Both are on Haq (The True Path). They do not differ in principle beliefs Belief. Their differences are in certain practical issues (such as Namaaz, wudhu etc and how these practices should be performed). Their differences are like that of Hanafi and Shafi'i etc. Both are on righteousness and one can not contradict one another.
Mas'ala (Rule): There is no increasing or lessening in Imaan. Only that which has form, shape, height, width and length can be increased or lessened and Imaan is pure of all these. Imaan is declaration and a declaration is a condition of submission. In certain verses of the Quran Allah azzawajal has mentioned enhanced Imaan. This refers to faith with true conviction in Imaan (It does not mean that the value of Imaan is more. It however does signify the strength of Imaan). In the time of the revelation of the Quran, there was no limit fixed for this. As the verses of the Quran were revealed, people brought Imaan on them the commands which were revealed. It is not such that the reality of Imaan increased or decreased. However, there is difference in the strength and weakness of Imaan of every individual (in other words the Imaan of some is stronger or weaker than that of others, meaning one has stronger or weaker faith than another). For example, the Imaan of Hazrat Abu Bakr Siddique (radi Allahu anhu) is stronger than the Imaan of the rest of the Ummats Imaan all put together.
Belief: There is no relationship between belief and unbelief. A person will either be a Muslim or a Kaafir. There is no third thing, that a person is neither a Muslim nor a Kaafir.
Mas'ala (Rule): Nifaaq (Hypocrisy), in other words to make the verbal claim of Imaan yet reject it in the heart is also kufr. The lowest level of Jahanum has been prepared for such people. There were also those in the time of the Prophet (sallal laahu alaihi wasallam) who were hypocrites. These hypocrites were exposed through verses of the Holy Quran and the Prophet (sallal laahu alaihi wasallam) with his vast knowledge recognised every one of them and said each one of them to be Munafiqs (hypocrites). Today, we can not call a person a Munafiq if he announces Islam and does not openly go against any principle beliefs, as we are not aware of his hearts condition. However, there are those misguided sects today who claim to be Muslims but reject the necessities of Deen as well.
Belief: Shirk means to make any than Allah worthy of worship and to accept more than one Allah being in existence. This is the worst form of kufr that one can commit. With the exception of this, any other Kufr, no matter how bad will not amount to Shirk. The command in the Quran that no shirk will be forgiven refers to all types of shirk and kufr. However, Allah azzawajal may forgive any other sins that he wills too (This is except kufr and shirk).�
Belief: One who commits major sin is still a Muslim and he will not be deprived of Jannat. This will be through the Grace of Allah and the intercession of the Holy Prophet (sallal laahu alaihi wasallam), or after getting some punishment for some of his deeds.
Mas'ala (Rule): Any person who makes dua for a kaafir after his death, or refers to a dead murtad (one who turns away from Islam) as 'Marhoom' or 'Maghfoor' or addresses a dead hindu as a heavenly soul is a kaafir.
Belief: To call a Muslim a Muslim and a Kaafir a Kaafir is from the necessities of Deen. To doubt the Kufr of any person who openly made kufr also causes one to become a kaafir. The law of Shariah is passed on that which is apparent and not that which is not known, for example if a Jew dies, then we will regard him as kaafir and will treat him as he should be treated after his death (not make dua for him etc.). If a Muslim dies and he did not openly reject any necessities of Deen, then we will treat him as a Muslim even after his death. There are those who say that we in the time we spend calling someone a kaafir, we should rather chant the name of Allah. Let us inform them that where have they seen us continuously chanting the words Kaafir, Kaafir. What we are saying, is that a kaafir must be called a Kaafir and a Muslim must be called a Muslim. They should not use their Sulah Qul (Compromising) tactics to put a veil over the kufr of any person.
source: http://www.islamieducation.com/en/islamic-faith/faith-iman-and-unfaith-kufr.html
