John Calvin Commentary Exodus 3:15

"And God said moreover unto Moses, Thus shalt thou say unto the children of Israel, Jehovah, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, hath sent me unto you: this is my name forever, and this is my memorial unto all generations." — Exodus 3:15 (ASV)

And God said moreover. God again assumes His name taken from the covenant He had made with Abraham and his descendants, so that the Israelites may know that they are not deceiving themselves in an uncertain God, provided they do not depart from the religion of their fathers. For just as soldiers assemble around their standard to maintain the order of their ranks, so He commands them to look back upon the special grace of their adoption, and to know that they are a people elected by God, because they are Abraham’s sons.

He confines them within these limits, so that they may not wander about in search of God. For we know that whatever opinions were held by the Gentiles regarding the Deity were not only entangled with many errors but were also ambiguous, so that they were always wavering concerning them. God demands another kind of religion from His people, on whose certainty their hearts may depend.

Besides, their long stay in the land of Egypt, although it had not destroyed the knowledge of the true God, had nevertheless greatly obscured that light of revelation that their fathers possessed. And again, the promise might seem to be obsolete when they had received no assistance while overwhelmed in such an abyss of misery. For this reason, the faith received from their fathers had undoubtedly grown cold.

Therefore, so that they may learn to rely on it, He calls Himself the God of their fathers and declares that by this title He will be celebrated forever. For I cannot consent to refer this to the previous expression, I am that I am, since the context does not permit it.

From this might be inferred the incomparable love of God towards His chosen people, because He had passed over all the nations of the earth and had bound Himself to them alone.

But we must remember that although it was honorable for Abraham and the patriarchs that God took His name from them, yet the main object of this was to confirm the truth of His promise.

There may be an apparent incongruity in saying, this is my memorial unto all generations, because a much more excellent memorial succeeded in the person of our Lord Jesus Christ. But my reply is that since, in the coming of Christ, the truth of the covenant made with Abraham was shown forth, and was thus demonstrated to be firm and infallible, its memory was renewed rather than destroyed; and that it thus still survives and flourishes in the Gospel, since Abraham even now does not cease to be the father of the faithful, under the one Head.

We conclude that God would not be spoken of on earth without the effects of His gratuitous adoption appearing, by which He may be proved to be faithful and true.