John Calvin Commentary Deuteronomy 33:29

"Happy art thou, O Israel: Who is like unto thee, a people saved by Jehovah, The shield of thy help, And the sword of thy excellency! And thine enemies shall submit themselves unto thee; And thou shalt tread upon their high places." — Deuteronomy 33:29 (ASV)

Happy are you, O Israel. He again exclaims that happy are the people whose salvation is in God; and surely this is the only true happiness; for unless we ascend to the first cause of Salvation, all salvations, so to speak, are merely transitory. And since God had honored the Israelites alone with this privilege, their condition is here distinguished from the common lot of the whole human race. By the words shield and sword is meant a perfect defense, which is to say that no part of their armor was to be sought elsewhere.