The Nullifiers of Islam are many and the scholars have collected them in books of Fiqh under the title, 'The Chapter of Riddah (Apostasy).' However, the most important of them are the following ten:
1. Shirk in the worship of Allah. Allah says, 'Verily! Allah forgives not (the sin of) setting up partners in worship with Him, but He forgives whom he pleases - sins other than that…' [Soorah an-Nisa (4): 116] and, 'Verily, whosoever sets up partners in worship with Allah, then Allah has forbidden Paradise for him, and the Fire will be his abode. And for the Zalimoon (polytheists and wrongdoers) there are no helpers' [Soorah al-Maida (5): 72] and it includes sacrificing for other than Allah, like tombs and jinn.
2. Setting up intercessors between oneself and Allah, invoking them, asking them for Shifa'ah and relying upon them. One who does this is considered a disbeliever by consensus.
3. He who does not declare the Mushrikeen (those who associate partners in worship with Allah) to be disbelievers, or doubts their disbelief, or approves their Madhhab (faith, creed) has disbelieved (in Allah).
4. Believing that the guidance of someone other than Allah's Messenger (sallalalhu alaihi wa-sallam) is more complete than his (sallalalhu alaihi wa-sallam) guidance, or that the ruling of other than him (sallalalhu alaihi wa-sallam) is better, like those who prefer the ruling of the tawagheet (pl. of Taghoot meaning things worshiped other than Allah) over the ruling of Allah's Messenger and they prefer the man-made laws to Islam.
5. He, who hates something from that which the Messenger came with, has disbelieved, even if he was acting upon it.
6. He, who mocks at something from the Religion of the Messenger, its rewards or punishments, has disbelieved. The proof of this is the Saying of Allah, 'Say, 'Was it at Allah, and His Ayat and His Messenger that you were mocking? Make no excuse, you have disbelieved after you had believed.' [(9): 65-66]
7. Magic and from among its types is causing unity and disunity among people (like that which causes separation of the husband from his wife or causes him to love her). He, who does this or is pleased with it, has disbelieved. The proof is the Saying of Allah, '…but neither of these two (angels) taught anyone (such things) until they had said, 'We are only for trial, so disbelieve not (by learning this magic from us).' [Soorah al-Baqarah (2): 102]
8. Aiding and cooperating with the Mushrikeen (disbelievers) against the Muslims. The proof is the Saying of Allah, 'And if any amongst you takes them as Awliya, then surely he is one of them. Verily, Allah guides not those people who are the Zalimoon (polytheists and wrongdoers and unjust).' [(5): 51]
9. He, who believes that some people can be excused from the Sharee'ah of Muhammad (sallalalhu alaihi wa-sallam), just like Khidr (alaihis-salaam) was not liable to the Sharee'ah of Moosa (alaihis-salaam), is a disbeliever.
This is just like what the extremist Sufis believe that they reach a stage (through their piety), where they are not in need of following the Messenger (sallalalhu alaihi wa-sallam).
10. Turning away from the Religion of Allah, neither learning it, nor acting upon it. The proof is the Saying of Allah, 'But those who disbelieve, turn away from that whereof they are warned.' [(46): 3] 'And who does more wrong than he, who is reminded of the Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) of his Lord, then he turns aside therefrom? Verily, We shall exact retribution from the Mujrimoon (criminals, disbelievers, polytheists, sinners, etc.).' [Soorah as-Sajdah (32): 22]
There is no difference if one does any of them (the above nullifiers) jokingly, seriously or in fear, except under force. They are all very dangerous and most likely to happen. So, it is necessary for a Muslim to be aware of them, and fear them for himself. And we seek Allah's protection from that which brings about His Anger and severe punishment.
2. Setting up intercessors between oneself and Allah, invoking them, asking them for Shifa'ah and relying upon them. One who does this is considered a disbeliever by consensus.
3. He who does not declare the Mushrikeen (those who associate partners in worship with Allah) to be disbelievers, or doubts their disbelief, or approves their Madhhab (faith, creed) has disbelieved (in Allah).
4. Believing that the guidance of someone other than Allah's Messenger (sallalalhu alaihi wa-sallam) is more complete than his (sallalalhu alaihi wa-sallam) guidance, or that the ruling of other than him (sallalalhu alaihi wa-sallam) is better, like those who prefer the ruling of the tawagheet (pl. of Taghoot meaning things worshiped other than Allah) over the ruling of Allah's Messenger and they prefer the man-made laws to Islam.
5. He, who hates something from that which the Messenger came with, has disbelieved, even if he was acting upon it.
6. He, who mocks at something from the Religion of the Messenger, its rewards or punishments, has disbelieved. The proof of this is the Saying of Allah, 'Say, 'Was it at Allah, and His Ayat and His Messenger that you were mocking? Make no excuse, you have disbelieved after you had believed.' [(9): 65-66]
7. Magic and from among its types is causing unity and disunity among people (like that which causes separation of the husband from his wife or causes him to love her). He, who does this or is pleased with it, has disbelieved. The proof is the Saying of Allah, '…but neither of these two (angels) taught anyone (such things) until they had said, 'We are only for trial, so disbelieve not (by learning this magic from us).' [Soorah al-Baqarah (2): 102]
8. Aiding and cooperating with the Mushrikeen (disbelievers) against the Muslims. The proof is the Saying of Allah, 'And if any amongst you takes them as Awliya, then surely he is one of them. Verily, Allah guides not those people who are the Zalimoon (polytheists and wrongdoers and unjust).' [(5): 51]
9. He, who believes that some people can be excused from the Sharee'ah of Muhammad (sallalalhu alaihi wa-sallam), just like Khidr (alaihis-salaam) was not liable to the Sharee'ah of Moosa (alaihis-salaam), is a disbeliever.
This is just like what the extremist Sufis believe that they reach a stage (through their piety), where they are not in need of following the Messenger (sallalalhu alaihi wa-sallam).
10. Turning away from the Religion of Allah, neither learning it, nor acting upon it. The proof is the Saying of Allah, 'But those who disbelieve, turn away from that whereof they are warned.' [(46): 3] 'And who does more wrong than he, who is reminded of the Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) of his Lord, then he turns aside therefrom? Verily, We shall exact retribution from the Mujrimoon (criminals, disbelievers, polytheists, sinners, etc.).' [Soorah as-Sajdah (32): 22]
There is no difference if one does any of them (the above nullifiers) jokingly, seriously or in fear, except under force. They are all very dangerous and most likely to happen. So, it is necessary for a Muslim to be aware of them, and fear them for himself. And we seek Allah's protection from that which brings about His Anger and severe punishment.
Nullifiers of Islam