Translation of the verse 6 from Surah Al-A‘la : Number of verses 19 - - page 591 - Part 30.
We shall make you to recite (the Quran), so you (O Muhammad (Peace be upon him)) shall not forget (it),
We will make you recite, [O Muhammad], and you will not forget,
(87:6) We shall make you recite and then you will not forget, *7
*7) Hakim has related from Hadrat Sa'd bin Abi Waqqas and Ibn Marduyah from Hadrat 'Abdullah bin 'Abbas that the Holy Prophet (upon whom be peace) repeated the words of the Qur'an for fear lest he should forget them. Mujahid and Kalbi say that even before Gabriel finished recitation of the Revelation the Holy Prophet would start repeating the initial verses lest he should forget them. Ou this very basis AIlah assured him that he should listen quietly when the Revelation was coming down, for, "We shall enable you to recite it; then you will remember it for ever. You should have no fear that you will forget any word of it. " This is the third occasion where the Holy Prophet (upon whom be peace) has been taught the method of receiving the Revelation. The first two occasions have been referred to in Ta Ha: 114 and Al-Qiyamah: 16-19 above. This verse proves that just as the Qur'an was sent down to the Holy Prophet as a miracle, so also its each word was preserved in his memory as a miracle and no possibility was allowed to remain that he should forget anything of it, or that he should utter another synonymous word for any word of it.
Source : Al-A‘la Verse 6: We will make you recite, [O Muhammad], and you will not forget,