What is the significance of Avraham calling the name of Har ha'Moriyah "Hashem Yir'eh"?
Rashi #1 (citing Targum Onkelos) and Targum Yonasan: He didn't just call it by this name; he Davenned that Hashem should accept it as the location of G-d-worship for his descendants, on which Hashem will rest His Shechinah there and appoint it as the location where they will bring Korbanos. 1
Targum Yonasan: He Davened that just as he had carried out the will of Hashem with a straight heart and joyfully, so too, should Hashem accept the Tefilos of Yitzchak's children when they come to pray there, and deliver them from their Tzaros.
Seforno: Refer to 22:14:2:4.
Da'as Zekenim: Initially it was a valley. Through Yir'ah (of Hashem, i.e. the Akeidah) it was raised; therefore it is called Har ha'Moriyah. 3
Because the ashes of Yitzchak are piled in a heap and stand to atone for K'lal Yisrael's sins.
Rosh: Why didn't David use the name of Shem or Avraham? He combined their names; the Vov is in place of Aleph and Hei, for they have the same Gematriya.
And what does it mean "that it will be said today b'Har Hashem Yera'eh"?
Rashi: That people in future generations will say on whichever day they are speaking, that Hashem appears to His people on this mountain.
Targum Onkelos: People will say how on this day Avraham worshipped Hashem on this mountain.
Targum Yonasan: People will say how on this day Avraham bound Yitzchak his son and that the Shechinah reveals Itself on it.
Seforno: The chosen mountain about which Yisrael said when the Torah was given that Hashem will appear on the Mountain of Hashem, which He will reveal it (in the time of David ha'Melech) - that is the mountain that Avraham called 'Hashem Yir'eh'.
Rashbam: From today and onwards, it will be said that this is the Mountain of Hashem on which Hakadosh-Baruch-Hu appeared to Avraham.
Hadar Zekenim: Avraham said, now that I did not offer my son, people will say that I obey Hashem's commands only when it benefits me - Hashem will see that their accusation is false.
Divrei Eliyahu: Avraham prayed that at a time of Churban, when we do not merit to see openly Hashem's protection, He will covertly guard us. Moshe wrote that today (when he wrote the Torah), we do see openly Hashem's protection.
Kol Eliyahu: Hashem wanted to make His dwelling below, but due sins of Adam, and... the Shechinah departed to the first... and ultimately to the seventh Raki'a. Avraham brought it back to the sixth, and prayed that it return to our land in the future. Indeed, it returned at Ma'amad Har Sinai, so Moshe wrote that today it is seen (here below).