John Calvin Commentary Joel 2:27

"And ye shall know that I am in the midst of Israel, and that I am Jehovah your God, and there is none else; and my people shall never be put to shame." — Joel 2:27 (ASV)

He repeats the same sentence, and in the beginning of the verse he explains what I have already said — that the miracle would be such as to compel the people to praise God. You shall know that I am in the midst of Israel: and this was the case, because God did not show His kindness to them in an ordinary way, and especially because it had been foretold, and also because this reason had been given — that God was mindful of His covenant.

The manner, then, in which He dealt with them, and further, the prediction itself, left the people no pretext for ignorance. Hence the Prophet now says, You shall know that I am in the midst of Israel, and still more, that I am Jehovah your God. By these words the Prophet reminds us that the deliverance of the people from their evils was to be wholly ascribed to the gratuitous mercy of God; for we have already seen that things would have been beyond hope, had not this consolation been added: You turn even now to me. The Prophet therefore repeats that there would be no other reason why God would deal so kindly with His people, and so mercifully spare them, but this: that He dwelt in the midst of Israel. But from where did this dwelling come, except that God had gratuitously chosen this people?

This indeed greatly helped to encourage the people; for how could they have hoped that God would be gracious to them, had they not been reminded of this truth that God was dwelling in the midst of them? Not because they were worthy, but because He deigned to come down to them.

He afterwards adds, And none else. By this sentence the Prophet more sharply urges them to return immediately to God; for if they delayed any longer, further delay would only lead to disappointment. So that the Jews, then, might not procrastinate as they usually did, he says that there is no other God; and thus he shows that there was no remedy for their evils, unless they sought to be reconciled to God.

There is then no God besides Me, and I dwell in the midst of you. The Lord claims all power for Himself, and then kindly invites the people to Himself, and for this reason — because He dwells in the midst of them. So that the people, then, might not form other expectations, God shows that all their hope was in Him alone. He further shows that salvation was not to be sought far away, provided the people had not forgotten the covenant that God was dwelling in the midst of them.