I will recompense—double— This phrase signifies, to punish with severity. See ch. Jeremiah 17:18 and Isaiah 40:2. The carcases of their detestable things, means their idols, which are called carcases, not only because they are without life, but also because of their being so detestable in the sight of God. See Lowth and Calmet.
Related Commentaries of Jeremiah 16:18
Jeremiah 16:18
18 And first I will recompense their iniquity and their sin double; because they have defiled my land, they have filled mine inheritance with the carcases of their detestable and abominable things.