Charles Spurgeon 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 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.

In crossing the desert, travelers raise little cairns of stone that they may be directed on a future occasion across that pathless sea of sand; and so God instructs them to set up waymarks and make high heaps, that they may know how to come back to him.