How can Hashem take Yisrael back in the future after He has divorced them and sent them out amongst the nations?
(32,1) “Listen, O heavens, and I will speak, and the earth shall hear the words of my mouth.”
The Sifri on this parsha says that in the future Yisrael will come to Hashem and say: Master of the World, You wrote in Your Torah “If a man sends away his wife and she goes from him and marries another man, may she return to him again?” (Yirmeyohu 3:1). Therefore, since You have sent us out to be amongst the nations how can You take us back again? Hashem will reply to them that it says in the posuk “if a man sends”, but “I am G-d and not a man” (Hoshea 11:9). House of Yisrael, are you divorced from Me? Does the posuk not say “Thus says Hashem: Where is your mother’s bill of divorce with which I sent her away?” (Yeshayohu 50:1).
This Midrash is a puzzle, but we can explain it according to the gemora in Gittin 77a which says that if the place to which a man throws a bill of divorce to his wife belongs to him, she is not divorced. This is what Hashem is saying: I am G-d and not a man, and therefore all the world is mine. Thus, there was never a divorce.