Alif, Lam, Ra. [This is] a Book whose verses are perfected and then presented in detail from [one who is] Wise and Acquainted.

(Quran-11:1)

It is He who has sent down to you, [O Muhammad], the Book; in it are verses [that are] precise - they are the foundation of the Book - and others unspecific. As for those in whose hearts is deviation [from truth], they will follow that of it which is unspecific, seeking discord and seeking an interpretation [suitable to them]. And no one knows its [true] interpretation except Allah . But those firm in knowledge say, "We believe in it. All [of it] is from our Lord." And no one will be reminded except those of understanding.

(Quran-3:7)

The Oldest Quran Found

The Language

And thus We have revealed it as an Arabic legislation. And if you should follow their inclinations after what has come to you of knowledge, you would not have against Allah any ally or any protector.

(Quran-13:37)

Discovery of The Oldest Quran Fragments

The Memorization

We will make you recite, [O Muhammad], and you will not forget,

Except what Allah should will. Indeed, He knows what is declared and what is hidden.

(Quran-87:6-7)

And the meaning of this statement: 'Thou shalt not forget', except as God wills what you should forget and don't remember it, They said: That is what Allah has abrogated from the Quran, so he lifted its wisdom and recitation. It is reported by Bashar on the authority of Yazid on the authority of Sa'eed, that Qutada said that Prophet Muhammad (peace be upon him) never forgot anything (except as God willed). And others reported: The meaning of forgetfulness in this context means 'abandonment' and they said: The meaning of the statement 'We shall make thee read', oh Muhammad so don't stop practicing any part of it except that which Allah commands you to stop practicing because it got abrogated. And those of the Arabic speaking language said regarding this: God did not will that the Prophet forget anything. And it is like Allah's similar statement 'Abiding therein, so long as the heavens and the earth endure, except as thy Lord may will. Surely, thy Lord does what HE pleases.' Surah 11: 107 and He does not will it. (Ibn Jarir al-Tabari, Jami' al-bayan fi ta'wil al-Qur'an, Commentary on Surah 87:7, Source)

[They will be] abiding therein as long as the heavens and the earth endure, except what your Lord should will. Indeed, your Lord is an effecter of what He intends.(Quran- 11: 107 )

Ibn Kathir states in his commentary...

Qatadah said, "The Prophet did not forget anything except what Allah willed.'' It has been said that the meaning of Allah's statement, (so you shall not forget,) is, "do not forget'' and that which would be abrogated, is merely an exception to this. (Tafsir Ibn Kathir, Source)

So we clearly see that the Prophet Muhammad (peace be upon him) did not forget any portions of the Quran that he was never meant to forget. As we see, one explanation for this verse is that God intended for the Prophet to forget the abrogated verses of the Qur'an. To understand more about abrogation, visit my section http://www.call-to-monotheism.com/qur_anic_variants and especially read this article http://www.call-to-monotheism.com/introduction_to_quranic_variants.

Source:http://www.call-to-monotheism.com/rebuttal_to_samuel_green_s_article__muhammad_s_perfect_memory___