Joel 2:13-14 KJV

11And 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?

12Therefore also now, saith the LORD, turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning:

13And 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.

14Who knoweth if he will return and repent, and leave a blessing behind him; even a meat offering and a drink offering unto the LORD your God?

15Blow the trumpet in Zion, sanctify a fast, call a solemn assembly:

16Gather the people, sanctify the congregation, assemble the elders, gather the children, and those that suck the breasts: let the bridegroom go forth of his chamber, and the bride out of her closet.