Joel 2:10-13

The earth shall quake before them; the heavens shall tremble: the sun and the moon shall be dark, and the stars shall withdraw their shining: and the LORD shall utter his voice before his army: for his camp is very great: for he is strong that executeth his word: for the day of the LORD is great and very terrible; and who can abide it? Therefore also now, saith the LORD, turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning: and rend your heart, and not your garments, and turn unto the LORD your God: for he is gracious and merciful, slow to anger, and of great kindness, and repenteth him of the evil.