Yahweh asks this question to emphasize what he has said. This can be stated in active form. Alternate translation: "You people of Israel certainly know that what I have said is true!" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Yahweh speaks of himself by name to express the certainty of what he is declaring. Alternate translation: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: [[rc://en/ta/man/translate/figs-123person]])