Now they who are bent on denying the Truth ask, "Why has not the Qur'an been revealed to him all at once?" So it has been! (It has all been revealed upon the Prophet's heart in the Night of Ruling (97:1)). For, in order to strengthen your heart We have already arranged it in the Right Order. And We have caused you to convey it to people in stages, step by step. (73:4).