Jesus' words and actions during his hidden life and public ministry were already salvific, for they anticipated the power of his Paschal mystery. They announced and prepared what he was going to give the Church when all was accomplished. The mysteries of Christ's life are the foundations of what he would henceforth dispense in the sacraments, through the ministers of his Church, for "what was visible in our Savior has passed over into his mysteries."
Source: Catechism of the Catholic Church (Vatican.va)