Therefore, if you bring your gift to the altar, and there recall that your brother has anything against you, leave your gift there at the altar, go first and be reconciled with your brother, and then come and offer your gift. (Mt 5:20-26)
https://bible.usccb.org/bible/readings/022324.cfm
This little verse from the Sermon on the Mount trips up all of us. Surely, the Lord doesn’t mean this, does He? But of course the Lord means exactly this—mercy before worship. This verse is also the origin of the Sign of Peace in the Eucharist.