Tafsiran Keluaran 17:15: Rashi, Chizkuni, Sforno & Rashbam

ויקרא שמו AND HE CALLED HIS (or its) NAME — the name of the altar,

ויבן שם מזבח, “he built an altar there; Moses built the altar at the bottom of Mount Chorev.

ויקרא שמו, he called the name of G’d in his prayer ה' ניסי. The matter is similar to the prophet Jeremiah saying in Lamentations 3,25: קראתי שמך ה'. Surely, there was nothing new in Jeremiah knowing the name of G’d. The point is that he addressed this attribute of G’d in that prayer. Moses addressed the attribute of G’d as the flag-bearer in Israel’s wars.

ה׳ נסי (lit., the Lord is my banner or my miracle) — The Holy One, blessed be He, here performed a miracle for us. It does not mean that the altar was named ה׳, “the Lord, my banner”, but the reason for so calling it was that anyone mentioning the altar’s name would thereby remember the miracle which the Omni-present had performed, since he would be saying: the Lord, He is our Miracle (cf. Rashi on Genesis 33:20).