5 Let no one therefore say, “I have not sinned against God, but against a brother. I have sinned against a man, it is a trifling sin, or no sin at all.” It may be, you say it is a trifling sin, because it is soon cured. You have sinned against a brother; give him satisfaction, and you are made whole. Thou did a deadly thing quickly, but quickly too have you found a remedy. Who of us, my Brethren, can hope for the kingdom of heaven, when the Gospel says, “Whosoever shall say to his brother, You fool, shall be in danger of hell fire?” Exceeding terror!
But behold in the same place the remedy: “If you bring your gift to the altar, and there rememberest that your brother has ought against you, leave there your gift before the altar.” God is not angry that you defer to lay your gift upon the Altar. It is you that God seeks more than your gift. For if you come with a gift to your God, bearing an evil mind against your brother, He will answer you, “You are lost, what have you brought Me? You bring your gift, and you are yourself no proper gift for God.
Christ seeks him whom He has redeemed with His Blood, more than what you have found in your barn.” So then, “Leave there your gift before the altar, and go your way, first be reconciled to your brother, and so you shall come and offer your gift.” Lo that “danger of hell fire,” how quickly dissolved it is! When you were not yet reconciled, you wast “in danger of hell fire;” once reconciled, you offer your gift before the altar in all security.
Source: Sermons on Selected Lessons of the New Testament (New Advent)