Bearing in mind the obligation to leave the presence of one's Rebbe backwards, how could Moshe, who was talking to Hashem face to Face, turn round before taking leave of Hakadosh-Baruch-Hu?
Refer to Sh'mos, 32:15:0.1:1.
Because Hashem instructed him to hurry - in Pasuk 12 - he had no option but to turn round, since it is impossible to hurry backwards.
Why does Moshe not refer to the Tefilah that he Davened before he descended Har Sinai and which Hashem accepted, until Pasuk 26?
Ramban: Because he first wanted to remind the people of the tremendous hassel that they caused him and the lengths to which he went to attain a pardon from Hakadosh-Baruch-Hu - to break the Luchos and to fall before Hashem for forty days and nights to Daven on behalf of both them and Aharon, with whom Hashem was extremely angry.
What is the significance of the fact that the mountain was "burning with fire"?