Jeremiah 15:20 - Ellicott's Commentary On The Whole Bible

I will make thee unto this people... — It is significant that the promise reproduced the very words which the prophet had heard when he was first summoned to his work (see Note on Jeremiah 1:18-19). Jehovah had not been unfaithful to His word, but, like all promises, it depended on implied conditions, and these the faint-hearted, desponding prophet had but imperfectly fulfilled. Let him “return” to the temper of trust, and there should be an abundant deliverance for him.