Yahweh uses this question to emphasize that the things that they are doing are so bad that he will no have mercy but will punish them. See how you translated a similar sentence in [Jeremiah 5:9](../05/09.md). Alternate translation: "So I will punish them, this is Yahweh's declaration. I will certainly get revenge for myself against them."(See: [[rc://en/ta/man/translate/figs-rquestion]])
Yahweh speaks of himself by name to express the certainty of what he is declaring. See how you translated this in [Jeremiah 1:8](../01/08.md). Alternate translation: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: [[rc://en/ta/man/translate/figs-123person]])