Moses built an altar, both for the offering of sacrifices of praise unto God, and to be a monument of this victory, and of the author of it. The name of it, viz. of the altar, which he so calls metonymically, because it was the sign and monument of Jehovah-nissi; even as circumcision is called God's covenant, Genesis 17:13, and the lamb, the passover, Exodus 12:11, and the cup, the new testament, Luke 22:20, because they were the signs of them. Or the word altar is to be repeated out of the former member, which is frequent, and the place to be is read thus, he called the name of it the altar of Jehovah-nissi. Or the name given to it signifies only the inscription engraven upon it, which was not the single name of God, but an entire sentence, the lord my banner. By which words he takes all the praise of the victory from the Israelites, and gives it to God.
Related Commentaries of Exodus 17:15
Exodus 17:15
15 And Moses built an altar, and called the name of it Jehovahnissi:c