And thou shalt swear, The LORD liveth, in truth, in judgment, and in righteousness; and the nations shall bless themselves in him, and in him shall they glory.
And thou - rather, And if (carried on from Jeremiah 4:1) thou shalt swear, "Yahweh liveth," in truth, etc. - i:e., if thou shalt worship, Him (for we swear by the God whom we worship, cf. Deuteronomy 6:13, "Thou shalt fear the Lord thy God, and serve Him, and shalt swear by His name;" Deuteronomy 10:20; Isaiah 19:18; Amos 8:14) in sincerity, etc.
And the nations - rather, this is apodosis to the 'if;' 'then shall the nations bless themselves in (by) Him' (Isaiah 65:16). The conversion of the nations will be the consequence of Israel's conversion (Psalms 102:13; Psalms 102:15; Romans 11:12; Romans 11:15).