Says the Shaykh Abu Ja’far: Our belief concerning this is that the Qur’an was sent down in one lot, in the month of Ramadan, on the Night of Power (laylatu’l-qadr) 1 (first) to al-Baytu’l-Ma’mur.2 And then it was revealed in the space of twenty3 years from the Baytu’l-Maqmur (to the Prophet).4
And verily Allah the Glorious and Mighty bestowed knowledge in its totality on His Prophet, on whom be the blessings of Allah and His peace, and then said to him: “…And hasten not (O Muhammad) with the Qur’an ere its revelation hath been perfected unto thee, and say: My Lord! Increase me in knowledge” (Qur’an 20:114).
And He said:
“Stir not thy tongue herewith to hasten it. Lo! Upon Us (resteth) the putting together thereof and the reading thereof. So when We read it, follow thou it’s reading. Then lo! Upon Us (resteth) the explanation thereof.” (Qur’an 75:16-19).