Matthew 5:23–24 — "Therefore, if you are offering your gift at the altar
and there remember that your brother or sister has something against
you, leave your gift there in front of the altar. First go and be
reconciled to them; then come and offer your gift."
The Catholic Sacrament of Reconciliation (also known as Penance, or Penance and Reconciliation) has three elements: conversion, confession and celebration. In it we find God's unconditional forgiveness; as a result we are called to forgive others.