Joel 2:12

We have here an earnest exhortation to repentance, inferred from that desolating judgment described and threatened in the foregoing verses: Therefore now turn you to the Lord. 1. "Thus you must answer the end and intention of the judgment; for it was sent for this end, to convince you of your sins, to humble you for them, to reduce you to your right minds and to your allegiance." God brings us into straits, that he may bring us to repentance and so bring us to himself. 2. "Thus you may stay the progress of the judgment. Things are bad with you, but thus you may prevent their growing worse; nay, if you take this course, they will soon grow better." Here is a gracious invitation, I. To a personal repentance, exercised in the soul, every family apart, and their wives apart, Zac 12:12. When the judgments of God are abroad, each person is concerned to contribute his quota to the common supplications, having contributed to the common guilt. Every one must mend one and mourn for one, and then we should all be mended and all found among God's mourners. Observe, 1. What we are here called to, which will teach us what it is to repent, for it is the same that the Lord our God still requires of us, we having all made work for repentance. (1.

— Matthew Henry's Concise Commentary (public domain)

With such judgments impending over the Jews, Jehovah Himself urges them to repentance. also now--Even now, what none could have hoped or believed possible, God still invites you to the hope of salvation. fasting . . . weeping . . . mourning--Their sin being most heinous needs extraordinary humiliation. The outward marks of repentance are to signify the depth of their sorrow for sin.

— Jamieson-Fausset-Brown Commentary (public domain)