Why did Avraham place the wood for the Korban on Yitzchak?
Oznayim la'Torah: The Midrash describes adorning the Korban with wood as a Hidur Mitzvah. 1 So Avraham adorned Yitzchak.
Oznayim la'Torah: Like those who brought Bikurim would adorn their baskets (See Mishnah, Bikurim 3:3).
Why is the Shechitah-knife called a 'Ma'acheles'?
Rashi #1: Because in a sense, it consumes the flesh, 1 (and because it prepares it for eating).
Peninim mi'Shulchan ha'Gra (4): This world cannot contain reward of a Mitzvah. We are fed only from the Zerizus of our Avos to do Mitzvos - Avraham rose early, saddled his donkey... Bereishis Rabah (56:1) cites "Yechayenu mi'Yomayim ba'Yom ha'Shelishi Yekimenu v'Nichyeh Lefanav" (Hoshe'a 6:2) - we eat the reward of his Zerizus on the first two days, but the reward of the Mitzvah itself on the third day remains for us in the world to come. (In Chulin 16a, it says that (perhaps) the Torah mentions the knife to show Avraham's Zerizus - PF.)
As we shall see at the end of the Parshah.
What is the significance of the phrase "And the two of them went together"?
Rashi: Avraham, who knew that he was going to sacrifice Yitzchak, went with the same Simchah as Yitzchak, who didn't!