12 So He said, "I will certainly be with you. And this shall be a sign to you that I have sent you: When you have brought the people out of Egypt, you shall serve God on this mountain."
Formerly Moses thought himself able to deliver Israel, and set himself to the work too hastily. Now, when the fittest person on earth for it, he knows his own weakness. This was the effect of more knowledge of God and of himself. Formerly, self-confidence mingled with strong faith and great zeal, now sinful distrust of God crept in under the garb of humility; so defective are the strongest graces and the best duties of the most eminent saints. But all objections are answered in, Certainly I will be with thee. That is enough. Two names God would now be known by. A name that denotes what he is in himself, I AM THAT I AM. This explains his name Jehovah, and signifies, 1. That he is self-existent: he has his being of himself. 2. That he is eternal and unchangeable, and always the same, yesterday, to-day, and for ever. 3. That he is incomprehensible; we cannot by searching find him out: this name checks all bold and curious inquiries concerning God. 4. That he is faithful and true to all his promises, unchangeable in his word as well as in his nature; let Israel know this, I AM hath sent me unto you. I am, and there is none else besides me. All else have their being from God, and are wholly dependent upon him. Also, here is a name that denotes what God is to his people. The Lord God of your fathers sent me unto you. Moses must revive among them the religion of their fathers, which was almost lost; and then they might expect the speedy performance of the promises made unto their fathers.
Matthew Henry's Commentary on Exodus 3:12
Commentary on Exodus 3:11-15
(Read Exodus 3:11-15)
Formerly Moses thought himself able to deliver Israel, and set himself to the work too hastily. Now, when the fittest person on earth for it, he knows his own weakness. This was the effect of more knowledge of God and of himself. Formerly, self-confidence mingled with strong faith and great zeal, now sinful distrust of God crept in under the garb of humility; so defective are the strongest graces and the best duties of the most eminent saints. But all objections are answered in, Certainly I will be with thee. That is enough. Two names God would now be known by. A name that denotes what he is in himself, I AM THAT I AM. This explains his name Jehovah, and signifies, 1. That he is self-existent: he has his being of himself. 2. That he is eternal and unchangeable, and always the same, yesterday, to-day, and for ever. 3. That he is incomprehensible; we cannot by searching find him out: this name checks all bold and curious inquiries concerning God. 4. That he is faithful and true to all his promises, unchangeable in his word as well as in his nature; let Israel know this, I AM hath sent me unto you. I am, and there is none else besides me. All else have their being from God, and are wholly dependent upon him. Also, here is a name that denotes what God is to his people. The Lord God of your fathers sent me unto you. Moses must revive among them the religion of their fathers, which was almost lost; and then they might expect the speedy performance of the promises made unto their fathers.