John Trapp on Jeremiah 31:21

Ver. 21. Set thee up way-markes] Statue tibi ſtatuas Mercuriales. q. d. I will ſurely bring thee back by the ſame way thou wenteſt hence into captivity: therefore take good notice of the way now, that thou maieſt know it again another time. This God ſaith to quicken their faith, and to aſcertain them of his love and ſavour: which is not like the winter-Sun, which caſteth a goodly countenance when it ſhineth, but giveth little heat and comfort, &c. We muſt alſo ſet up way-markes, obſerve how we fell from the Lord, repent and do our firſt works.

Set thine heart towards the high-way] This is done ſaith Auſtin, when God is ſought for Gods ſake: ſed vix diligitur Jeſus propter Jeſum, ſaith the ſame Father, but this is rearely done.