All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Faith is an utterance by the tongue, a confession (affirmation) by the heart, and actions with the limbs. Ahlus-Sunnah agree in consensus that confession by the heart or by the tongue is of no avail if there is no action of the heart, which is loving by the heart and the abiding of the heart (by the commandments), in the same manner that the confession by the heart did not benefit Satan, Pharaoh and his people, the Jews, and the polytheists who believed that the Prophet is the truth. Moreover, they used to affirm this secretly and openly, and they said, “He is not a liar, but we do not follow him and we do not believe in him.”
Imaam Ibn Al-Qayyim said in his book about the prayer and the ruling on someone who abandons it:
“We say that faith is an affirmation (confession), but affirmation is not just believing that the news is true without abiding by it, because if believing in its truth alone would constitute faith, then Satan, Pharaoh and his people, the people of Prophet Saalih, the Jews who knew that Muhammad was the Prophet of Allaah in the same manner as they knew their children would all be believers then.
Allaah says (what means): {And indeed, they do not call you untruthful}, i.e. they do believe that you are truthful, {but it is the verses of Allaah that the wrongdoers deny.} [Quran 6:33] Denial is after knowing the truth.
Allaah says (what means): {And they rejected them, while their [inner] selves were convinced thereof, out of injustice and haughtiness.} [Quran 27:14] Also, Moosa (Moses) said to Pharaoh: {...You have already known that none has sent down these [signs] except the Lord of the heavens and the earth as evidence.} [Quran 17:102] besides, Allaah said about the Jews: {Those to whom We gave the Scripture know him as they know their own sons. But indeed, a party of them conceal the truth while they know [it].} [Quran 2:146]
What is even stronger as evidence is when the two Jewish men came to the Prophet and asked him for the evidence about his prophecy; they said, ‘We bear witness that you are a Prophet.’ He said, ‘What prevents you from following me?’ They replied that Prophet Daawood (David) had supplicated that there would come from among his descendants a Prophet and that they feared that if they would follow him, the Jews would kill them. So these two men confessed with their tongues a confession that is identical to their belief that he (Prophet Muhammad ) was a Prophet, but they did not enter faith with this confession and acknowledgment because they did not abide by his obedience and his orders.
This is the same thing with the disbelief of Abu Taalib; he really and perfectly knew the fact that the Prophet was truthful and he confessed this by his tongue and declared this in his poems, but he did not enter Islam by this confession.
Confession (or affirmation) is fulfilled by two matters: firstly, believing in the truthfulness, and secondly: the love with the heart and abiding by what it believes in and loves. It is for this reason that Allaah said to Ibraaheem (Abraham): {We called to him: O Ibraaheem, You have fulfilled the vision.} [Quran 37:104-105] Ibraaheem believed in the truthfulness of his vision from the moment he saw the vision because the vision of the Prophets is revelation, but he did what he was ordered to do after he believed in it.”
Therefore, it should be known that if someone abandons actions under the requirement of the Two Testimonies of Faith, then he is not considered a believer because Allaah negated faith from the one who did not abide by His ruling and did not submit himself to His legislation (the sharee'ah); Allaah says (what means): {But no, by your Lord, they will not [truly] believe until they make you [O Muhammad] judge concerning that over which they dispute among themselves and then find within themselves no discomfort from what you have judged and submit in [full, willing] submission.} [Quran 4:65]
Allaah also says (what means): {But the hypocrites say: We have believed in Allaah and in the Messenger, and we obey; then a party of them turns away after that. And those are not believers.} [Quran 24:47]
Shaykh Ibn Taymiyyah said, “Allaah negated the faith from those who turned away from acting, even if they fulfilled the requirement of uttering by the tongue.”
In another context, he said:
“It is not possible that a man believes a firm belief in his heart that Allaah ordained him to pray, to pay zakah, to fast, and to perform Hajj while he spends his whole life not prostrating one single prostration to Allaah, he does not fast the month of Ramadan, does not pay the zakah that Allaah imposed on him, and does not perform the pilgrimage to the House of Allaah; then this is not possible, and this can only happen by being hypocrite in one’s heart, and not with the existence of true faith. If is for this reason that Allaah described those who refused to prostrate as disbelievers; as in the verse in which Allaah says (what means): {The Day the shin will be uncovered and they are invited to prostration but the disbelievers will not be able. Their eyes humbled, humiliation will cover them. And they used to be invited to prostration while they were sound.} [Quran 68: 42-43]”
For more benefit, please refer to fatwa 91651.
Allaah knows best.