Why the double expression "Don't stretch out your hand against the lad and don't do anything to him"?
Rashi: After the first command - not to Shecht Yitzhak, Avraham asked that he should at least be permitted to make a cut, so that his journey should not have been in vain, the angel added the second. 1
Hadar Zekenim: The angels' tears blunted the knife, so Avraham said that he can choke him.
Rashi: "Me'umah" is a Lashon 'Mum'
What did Hashem mean when He said "Atah Yada'ati ... "? Didn't He know before?
Rashi: Hashem's statement here was in response to Avraham's query, as to why He first ordered him to sacrifice Yitzchak, in spite of having promised him "Ki ve'Yitzchak Yikarei L'cha Zara"; and now He ordered him to desist? To which Hashem replied that He never intended him to sacrifice Yitzchak in the first place, only to test him, to prove to the Satan and to the nations of the world why Hashem loved him so. And now that this had been achieved, he could untie him and take him down.
Rashbam: He was now able to publicize to the world that he (Avraham) was a G-d-fearing man. 3
Seforno: It was the angel who now knew that Hashem was justified in raising Avraham above the level of the angels. 4
Kol Eliyahu, Divrei Eliyahu: Before, he served with mercy; now he served with cruelty, the opposite Midah. 5 The Torah promises long life regarding two Mitzvos - Kivud Av v'Em and Shilu'ach ha'Kan, which require mercy and cruelty. (If one says that Hashem had mercy on the bird's nest, we silence him.) Serving with one Midah is no proof of Yir'as Shamayim. Perhaps he has that Midah naturally!
Mishnas R. Aharon 1 p.111: Avraham passed the test of the Akeidah due to Yiras Hashem. Mesiras Nefesh is through love - "v'Ahavta... uv'Chol Nafshecha." However, for some matters love is not enough; fear is needed.
Lev Eliyahu (Bereishis p.69): After all Avraham's attributes and tests, and he passed all of them, Yir'as Hashem was primary.
Since the word "Mimeni" refers to "Yerei Elokim" - meaning that Avraham was a greater Yerei Elokim than they are, like it says in Sanhedrin (93a) 'Tzadikim are greater than the angels'.
Only below (Pasuk 16), it says "Ne'um Hashem". This implies that here, the angel spoke for himself. If so, why did he say "(you did not hold back your son) from me"?
Kol Eliyahu, Divrei Eliyahu: Every Mitzvah creates an angel, according to the level of love, Zerizus, fear and intent. The angel created by the Akeidah said "I know that you fear Hashem... from me" (I have a great level, due to your great Yir'as Hashem).
Refer to 22:12:2:4*.