Translation of the verse 7 from Surah Al-A‘la : Number of verses 19 - - page 591 - Part 30.
Except what Allah, may will, He knows what is apparent and what is hidden.
Except what Allah should will. Indeed, He knows what is declared and what is hidden.
(87:7) except what Allah should wish. *8 He knows all that is manifest and all that is hidden. *9
*8) This sentence can have two meanings: first, "that the preservation of the entire Qur'an word for word in your memory is not a manifestation of your own power but the result of Allah Almighty's bounty and grace; otherwise if Allah so willed, He could cause it to be forgotten. " This same theme has been expressed at another place in the Qur'an, thus: "O Muhammad! We may, if We so will, take back from you all of what We have revealed to you." (Bani Isra'il: 86). Another meaning also can be: "Your forgeting something temporarily, or your forgetting a verse or a word occasionally is an axception froth this promise. What has been promised is: `You will not forget any word of the Qur'an permanently'." This meaning is confirmed by the following tradition of Bukhari: Once while leading the Fajr Prayer the Holy Prophet (upon whom be peace) happened to omit a verse during the recitation. After the Prayer hadrat Ubayy bin Ka`b asked if the verse had been abrogated. The Holy Prophet replied that he had forgotten to recite it.
*9) Although the words are general, and they mean that Allah knows everything, whether it is open or hidden, yet in the context in which they occur, they seem to mean: "O Prophet, your reciting the Qur'an along with Gabriel (peace be on him) is known to Allah and your fear for which you do so is also in Allah's knowledge. " Therefore, the Holy Prophet is being assured that he will not forget it.