John Calvin Commentary Exodus 4:27

"And Jehovah said to Aaron, Go into the wilderness to meet Moses. And he went, and met him in the mountain of God, and kissed him." — Exodus 4:27 (ASV)

And the Lord said to Aaron. When, from the long lapse of time, Aaron must have supposed that his brother had died in exile, he now receives the joyful announcement from the mouth of God that he is alive. Not only so, but he is also excited with the hope of His special favor. For, although God does not explain in detail what he had decreed to do and prepared, yet, by His revelation, He promises him something unusual and unexpected.

But the brevity of the command is remarkable, for God says nothing about the deliverance but desires him to be the disciple of his younger brother. And although, by his promptitude, he manifested the greatest zeal and anxiety to obey, still he is not put on an equality with Moses, who is slow, dubious, vacillating, and almost supine; but he is commanded to learn from him the design of God.

However, so that he would not question his own and his brother’s vocation, he is instructed by a divine vision that God is the author of the whole transaction. This serves to confirm the verbal information he is to receive.

For although Aaron was the messenger of God and the instrument of the Holy Spirit, we still see that he was not exempt from the usual condition to which we are subjected: hearing God’s word from the mouth of man.

If, then, there are any who object to being taught through a human voice, they are not worthy to have God as their Teacher and Master. For it is soon after added that Moses related all that was commanded him, as well as the great power to work miracles that had been delegated to him.

But Aaron himself, although the elder, not only paid honor to his brother, whom he knew to be a Prophet of the Lord, but also willingly submitted himself to him as if to an angel. The kiss is mentioned as a sign of recognition, by which he testified to the firmness of his faith.