Exodus 3:13

They shall say - What is his name? - Does not this suppose that the Israelites had an idolatrous notion even of the Supreme Being? They had probably drank deep into the Egyptian superstitions, and had gods many and lords many; and Moses conjectured that, hearing of a supernatural deliverance, they would inquire who that God was by whom it was to be effected. The reasons given here by the rabbins are too refined for the Israelites at this time. "When God," say they, "judgeth his creatures, he is called אלהים Elohim; when he warreth against the wicked, he is called צבאות Tsebaoth; but when he showeth mercy unto the world, he is called יהוה Yehovah." It is not likely that the Israelites had much knowledge of God or of his ways at the time to which the sacred text refers; it is certain they had no written word. The book of Genesis, if even written, (for some suppose it had been composed by Moses during his residence in Midian), had not yet been communicated to the people; and being so long without any revelation, and perhaps without even the form of Divine worship, their minds being degraded by the state of bondage in which they had been so long held, and seeing and hearing little in religion but the superstitions of those among whom they sojourned, they could have no distinct notion of the Divine Being. Moses himself might have been in doubt at first on this subject, and he seems to have been greatly on his guard against illusion; hence he asks a variety of questions, and endeavors, by all prudent means, to assure himself of the truth and certainty of the present appearance and commission. He well knew the power of the Egyptian magicians, and he could not tell from these first views whether there might not have been some delusion in this case. God therefore gives him the fullest proof, not only for the satisfaction of the people to whom he was to be sent, but for his own full conviction, that it was the supreme God who now spoke to him.

What is his name - The meaning of this question is evidently: "By which name shall I tell them that the promise is confirmed?" Each name of the Deity represented some aspect or manifestation of His attributes (compare the introduction to Genesis). What Moses needed was not a new name, but direction to use that name which would bear in itself a pledge of accomplishment. Moses was familiar with the Egyptian habit of choosing from the names of the gods that which bore specially upon the wants and circumstances of their worshippers, and this may have suggested the question which would be the first his own people would expect him to answer.

3:13 When they shall say to me, What is his name? What shall I say unto them? - What name shall I use, whereby thou mayest be distinguished from false gods, and thy people may be encouraged to expect deliverance from thee?