At the Last Supper Jesus anticipated the free offering of his life
Jesus gave the supreme expression of his free offering of himself at the meal shared with the twelve Apostles "on the night he was betrayed". On the eve of his Passion, while still free, Jesus transformed this Last Supper with the apostles into the memorial of his voluntary offering to the Father for the salvation of men: "This is my body which is given for you." "This is my blood of the covenant, which is poured out for many for the forgiveness of sins."
Source: Catechism of the Catholic Church (Vatican.va)