When 3:102 was revealed, Umar ibn Al-Khattaab, may God have been pleased with him, cried and said, "God has just ordered us to do the impossible!" The prophet, peace be upon him smiled at that remark but said nothing. Then, when 64:16 was revealed, Umar breathed a sigh of relief!
That is probably the basis for those who claim that 64:16 abrogated 3:102. Let's examine that.
is claimed to have been abrogated by
The abrogation case here is that 3:102 mandates that we watch out for God as He ought to be watched out for, which, as Umar concluded, would be impossible, but would it? Remember, the prophet was amused by Umar's interpretation which tells me that he found it interesting. Indeed, no one can properly watch out for God because our abilities are finite and God's attributes are limitless.
The question to ask then to determine whether there is abrogation here is this: Is watching out for God as best we could the same as watching out for God as He ought to be watched out for? I say yes! That's because God tells us that He never mandates anything that is beyond our capacity,
So when He mandated that we watch out for Him as He ought to be watched out for, He mandated something that we can do
. Muhammad Al-Khudhari (Bek) agrees with me on this, in his book أصول الفقه, page 253.
Dr. Mustafa Zayd's refutation of this claim, on pages 116-117 (item 847) of volume 2 of his book النسخ في القرآن الكريم, is that 64:16 is an elaboration of the vague (تفسير المبهم). He quotes a few important quotes from scholars,
Abu-Ja`far An-Nahhaas wrote:
The abrogating is what contradicts the abrogated from all of its angles, rescinding it, removing its ruling.
Ibn `Aqeel wrote:
Whoever calls the elaboration in the Quran abrogation is mistaken.
Ibn Al-Jawzi wrote:
This is called elaboration of puzzling text (بيان مشكل). Folks thought that this is requiring what cannot be done, so God removed their puzzlement.
If He said, "Do not watch out for Him as He ought to be watched out for", then that would have been abrogation. Instead, He explained that what He means by "ought to" does not include what is beyond one's capacity.