Matthew Henry Commentary Jeremiah 3:21-25

"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. Return, ye backsliding children, I will heal your backslidings. Behold, we are come unto thee; for thou art Jehovah our God. Truly in vain is [the help that is looked for] from the hills, the tumult on the mountains: truly in Jehovah our God is the salvation of Israel. But the shameful thing hath devoured the labor of our fathers from our youth, their flocks and their herds, their sons and their daughters. Let us lie down in our shame, and let our confusion cover us; for we have sinned against Jehovah our God, we and our fathers, from our youth even unto this day; and we have not obeyed the voice of Jehovah our God." — Jeremiah 3:21-25 (ASV)

Sin is turning aside to crooked ways. And forgetting the Lord our God is at the bottom of all sin. By sin we bring ourselves into trouble. The promise to those who return is, God will heal their backslidings, by his pardoning mercy, his quieting peace, and his renewing grace.

They come devoting themselves to God. They come disclaiming all expectations of relief and help from anyone but the Lord. Therefore, they come depending only on him. He is the Lord, and only he can save. It points to the great salvation from sin Jesus Christ accomplished for us.

They come justifying God in their troubles, and judging themselves for their sins. True penitents learn to call sin shame, even the sin they have been most pleased with. True penitents learn to call sin death and ruin, and to blame it for all they suffer. While people harden themselves in sin, contempt and misery are their portion: for whoever covers his sins will not prosper, but whoever confesses and forsakes them will find mercy.