en_tn/jer/33/20.md

The word of Yahweh came to Jeremiah, saying, "Yahweh

Yahweh says

Yahweh is speaking of himself here. AT: "I say" (See: rc://en/ta/man/translate/figs-123person)

my covenant with day and night ... my covenant with David my servant

No one can change day and night, and no one can change God's covenant with David.