Mortal sin

A mortal sin (Latin: peccātum mortāle), in Christian theology, is a gravely sinful act which can lead to damnation if a person does not repent of the sin before death. It is alternatively called deadly, grave, and serious; the concept of mortal sin is found in both Catholicism and Lutheranism. A sin is considered to be "mortal" when its quality is such that it leads to a separation of that person from God's saving grace. Three conditions must together be met for a sin to be mortal: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent." The sin against the Holy Spirit and the sins that cry to Heaven for vengeance are considered especially serious. This type of sin is distinguished from a venial sin in that the latter simply leads to a weakening of a person's relationship with God. Despite its gravity, a person can repent of having committed a mortal sin. Such repentance is the primary requisite for forgiveness and absolution.

Teaching on absolution from sins is varied somewhat throughout Christian denominations. The teaching for Catholics on the sacrament of confession and the act of contrition for absolution was declared a mandatory catholic belief in the Council of Trent. Confession and Absolution is practiced in Lutheran churches, with it being historically held on Saturdays in preparation for Mass on the Lord's Day.