Restoration of Israel and the nations is inevitable because, ultimately, it is the Lord who will do it. The passage ends with the Lord saying, Therefore, behold, I will make them know, this once I will make them know my power and my might, and they shall know that my name is Lord.
The question can be asked, Who is the Lord speaking these words about? Israel or the nations?
In the context of the whole passage (Jeremiah 16:14–21), the covenant promise of Israel (Jeremiah 16:14–15) and the nations (Jeremiah 16:19–20) turning to the Lord is affirmed, which suggests that them
in Jeremiah 16:21 could be referring to both Israel and the nations. In the more immediate context of Jeremiah 16:19–21 the word them
in Jeremiah 16:21 seems to be referring to the nations. However, it may not be necessary to be too precise since in the overall story of redemption the Lord will draw both Israel and the nations to himself by revealing his power and might to both, not just through acts of redemption, but through powerful acts of judgment that lead to redemption. In the end, the Lord will cause both Jew and Gentile to know that my name is Lord.
Included in these acts of judgment and redemption are the Exodus and return from exile, but pre-eminently it is the death and resurrection of the Christ that reveals the Lord to his world and causes people, Jew and Gentile, to turn from false gods to the one true living God.
21 “Therefore, behold, I will make them know, this once I will make them know my power and my might, and they shall know that my name is the LORD.”