I am the LORD thy God, which brought thee out of the land of Egypt: open thy mouth wide, and I will fill it.
I am the Lord thy God, which brought thee out of the land of Egypt - strongest motive for obeying the command in Psalms 81:9, to have no strange god; for none else except Yahweh was Israel's Deliverer (cf. Deuteronomy 32:12).
Open thy mouth wide, and I will fill it - i:e., I will satisfy abundantly all thy desires, because I am rich for all thy needs (Psalms 81:14-16; Romans 10:12; Philippians 4:19). You have no necessity to apply to any strange god, because you have all things in ME (Genesis 15:1; Psalms 16:5).