first ... double - Horsley translates, “I will recompense ... once and again”; literally, “the first time repeated”: alluding to the two captivities - the Babylonian and the Roman. Maurer, “I will recompense their former iniquities (those long ago committed by their fathers) and their (own) repeated sins” (Jer 16:11, Jer 16:12). English Version gives a good sense, “First (before ‘I bring them again into their land’), I will doubly (that is, fully and amply, Jer 17:18; Isa 40:2) recompense.”
carcasses - not sweet-smelling sacrifices acceptable to God, but “carcasses” offered to idols, an offensive odor to God: human victims (Jer 19:5; Eze 16:20), and unclean animals (Isa 65:4; Isa 66:17). Maurer explains it, “the carcasses” of the idols: their images void of sense and life. Compare Jer 16:19, Jer 16:20. Lev 26:30 favors this.