מדרש על שמות 4:21

(Exod. 4:21:) THEN THE LORD SAID UNTO MOSES: WHEN YOU GO TO RETURN TO EGYPT. The Holy One showed him the miracles that he was going to do for him. Now he had said to him (Exod. 3:16:): GO AND GATHER THE ELDERS OF ISRAEL,… and afterwards you are going to Pharaoh. Moses said: If they should say TO ME (in Exod. 3:13), WHAT IS HIS NAME, WHAT DO I SAY TO THEM? He said to him: Say to them (in vs. 14): I AM THAT I AM.