penance (pĕnˈəns) [key], sacrament of the Roman Catholic and Orthodox Eastern churches. By it the penitent (the person receiving the sacrament) is absolved of his or her sins by a confessor (the person hearing the confession and conferring the sacrament). Every Catholic is required to confess all his or her mortal (serious) sins before receiving communion and at least once a year. A penitent need confess only sins committed since baptism or since his or her last confession. To make the sacrament valid the confessor must be a priest and the penitent must be contrite and possess a firm purpose of amendment. Sins inadvertently forgotten after a careful examination of conscience are included in the absolution. Before granting absolution, the confessor, acting as an instrument of both God and the Church, may admonish the sinner, and he imposes a penance (a punishment, usually consisting of prayers). The penitent is required to make restitution for injuries to others. According to a canon of the Council of Trent, Jesus instituted this sacrament when he first appeared to the disciples after the resurrection (John 20.19–23). Following the Second Vatican Council, the Roman Catholic Church introduced the liturgy for a new communal penitential service, during which the individual has the opportunity to confess privately to a priest. Absolution is still granted only on an individual basis. In the Eastern churches confession is required before communion, but there has been no development of moral theology or of casuistry comparable to that of the West. The priest acts in the sacrament only as an instrument of God, who forgives sins by the sacrament.