Joel 2:15 - Albert Barnes' Notes on the Bible

Before, he had, in these same words Joel 2:1; Joel 1:14, called to repentance, because the Day of the Lord was coming, was near, “a day of darkness,” etc. Now , because God is “gracious and merciful, slow to anger and plenteous in goodness,” he agains exhorts, “Blow ye the trumpet;” only the call is more detailed, that every sex and age should form one band of suppliants to the mercy of God. : “Most full abolition of sins is then obtained, when one prayer and one confession issueth from the whole Church. For since the Lord promiseth to the pious agreement of two or three, that He will grant whatever is so asked, what shall be denied to a people of many thousands, fulfilling together one observance, and supplicating in harmony through One Spirit?” “We come together,” says Tertullian of Christian worship, “in a meeting and congregation as before God, as though we would in one body sue Him by our prayers. This violence is pleasing to God.”