Holy Orders and Matrimony are called sacraments in service of the community because they confer a specific mission on their recipients to build up the people of God. Through the service they render to others, they contribute to the salvation of those who receive them. Christ instituted the sacrament of Holy Orders at the Last Supper when he conferred on the Apostles and their successors in the priesthood the power to consecrate and offer his Body and Blood in the Mass.