Tafsir of Al-A'la 87:7

إﻻ ما شاء الله

Except what Allah may will. Qatadah said, "The Prophet did not forget anything except what Allah willed.'' It has been said that the meaning of Allah's statement,

فﻼ تنسى

(so you shall not forget,) is, "do not forget'' and that which would be abrogated, is merely an exception to this. Meaning, `do not forget what We teach you to recite, except what Allah wills, which He removes and there is no sin on your leaving it off (not retaining it).' Concerning Allah's statement,

إنه يعلم الجهر وما يخفى

He knows what is apparent and what is hidden. meaning, He knows what the creatures do openly and what they hide, whether it be statements or deeds. None of that is hidden from Him. Then Allah says,

ونيسرك لليسرى