The latter part of this verse expounds the former. Thou shalt (saith God) return again to these cities which thou now leavest, therefore take good notice of the way thou seest, set up some marks by which thou mayst know it again; make thee pillars of some high heaps of stone in the way, which thou mayst know again when thou comest at them; mind well the way that the Assyrians and the Babylonians carried thee, for thou shalt come back the same way. Further to assure them they should return, he calls to them to turn again, and doubleth his words, for the further confirmation of the thing.
Related Commentaries of Jeremiah 31:21
Jeremiah 31:21
21 Set thee up waymarks, make thee high heaps: set thine heart toward the highway, even the way which thou wentest: turn again, O virgin of Israel, turn again to these thy cities.