Albert Barnes Commentary Jeremiah 3:21

"A voice is heard upon the bare heights, the weeping [and] the supplications of the children of Israel; because they have perverted their way, they have forgotten Jehovah their God." — Jeremiah 3:21 (ASV)

Upon the high places - Upon those bare table-lands, which previously had been the scene of Israel’s idolatries (Jeremiah 3:2). The prophet supposes the offer of mercy to Israel if repentant to have been accepted, and describes Israel’s agony of grief now that she is convinced of her sins.

Weeping and supplications - literally, “the weeping of earliest prayers for mercy.”

For they have ... - Rather, because they have perverted their way, literally, made it crooked. It gives the reason for their cry for mercy.