“We have revealed the Qur’ān in parts that you may recite it to people slowly and with deliberation; and (for that reason) We have revealed it gradually [to suit particular occasions]. Tell them, (O Prophet!): ‘Believe in it, or do not believe’; when it is recited to those who were given the knowledge before its revelation, they fall down upon their faces in prostration, and say: ‘Glory be to our Lord. Surely the promise of our Lord was bound to be fulfilled.’ And they fall down upon their faces, weeping, and their humility increases when they hear recitation of the Qur’ān.
(Al-Qur’ān – 17:107-109)
That the Qur’ān was revealed gradually rather than in one piece does not prove any deficiency in God’s knowledge or wisdom. It is rather man’s power of comprehension and assimilation which is deficient. Hence, if the Qur’ān had been revealed in one piece, it would have been difficult for people to assimilate its whole message in a short span of time. Nor would it have been easy to fully digest even a single aspect of that message in a limited period of time. Thus God, in His wisdom, entrusted Gabriel to communicate the Qur’ān to the Messenger (peace and blessings of Allah be to him) in pieces. At times, the Qur’ānic messages were set out succinctly and at other times in some detail. All this is done so that all those who seek the truth might be able to obtain it despite their varying intellectual endowments, and subsequently grow mature in their knowledge, conviction and understanding.