Or HaChaim on Ki Sisa 33:2

English: ושלחתי לפניך מלאך , "and I will send an angel ahead of you, etc." It is clear from this verse that up until now G'd had meant for Moshe personally to lead the children of Israel into the Holy Land and to distribute it to them. We have a line in Exodus 6,1 where G'd told Moshe: עתה תראה "now you will see," and many commentators understood this to mean that Moshe would be a witness only to the Exodus from Egypt but not to the conquest of the land of Canaan. Perhaps G'd had cancelled that decree in consideration of how Moshe had interceded on behalf of the Jewish people, putting his own future on the line.