The interpretation of "قدير"
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Sheikh Muhammad Mostafa Abu-Al'ila and Imam Muhammad Abduh interpret the use of "قدير" (most capable) in 2:106 as supporting the interpretation of آية as 'sign' rather than 'verse', saying that another description along the lines of wisdom or knowledge would have been more befitting if the intended meaning was 'verse'. They have a point, but upon closer inspection I respectfully disagree since the use of the description "قدير" is not about a verse per se, but about a better verse.
I fully agree with you. God's capability which He asserts in 2:106 is in bringing signs that are ever more impressive than their antecedents. A convert to Islam, who used to be a pastor and studied the bible closely, wrote online that the Hebrew bible, the Tanakh, contains very eloquent verses and others that are sloppy, but that the Quran is outstanding prose that is superior to anything that he has ever read before.
The interpretation of نسي...
Al-Jabri addresses the issue of (ننسها) on pages 161-162 of
his book. He argues against the possibility of the Prophet (PBUH) forgetting a Quranic revelation. I am not sold on his argument, but he makes one point worth mentioning here.
The argument is about a non-existent issue. Verse 2:106 does not say that verses will be forgotten, rather it says that verses will be
caused to be forgotten. In other words, it's not human tendency but God's willful action.
Alternative interpretation...
Al-Jabri offers an entirely different interpretation of 2:106 and 16:101 on pages 164-165 of
his book. He interprets the 'substitution' that 16:101 is talking about as reordering the verses in the Quran without eliminating any. He argues that the Prophet (PBUH) gave instructions for each verse as to where it belongs, and the substitution amounts to changing where the older verses belong upon the revelation of new verses.
He extrapolates this to 2:106 saying that نسخ means the same thing. He provides linguistic evidence! The origin of the word نسخ comes from the bees moving the honey from one cell to another. He goes on to substantiate his interpretation by mentioning that both the Quran and the honey were described as شفاء in different verses!
If we actually apply the honey semantic, we might argue that
ننسخ means that God has moved His sign, the Book, from the Hebrews to the Arabs
As for
ننسها that would apply to the scrolls of Abraham (PBUH).