Charles Ellicott Commentary Jeremiah 31:21

"Set thee up waymarks, make thee guide-posts; set thy heart toward the highway, even the way by which thou wentest: turn again, O virgin of Israel, turn again to these thy cities." — Jeremiah 31:21 (ASV)

Set thee up way marks ... —It will be noted that the figure is changed, and that instead of “Ephraim, the dear son,” we have Israel, the “backsliding daughter.” The idea of the return of the exiles is still prominent, and she, as represented by the first group of those who came back, is called on to set up “heaps of stones,” like Eastern travelers, as waymarks for those who followed . The way she had trod when she was led out into captivity was to be retrod in the fullness of joy on her return. She was to pass in her joy through the very same cities that had then seen her in her shame.