The sacraments are referred to as actions of Christ because (1) by means of them, Christ gives His Spirit to all who believe in Him, and (2) it is from Christ that the sacraments receive the power to make men holy.
1. Sacraments are called actions of Christ because, by means of them, Christ gives His Spirit to all who believe in Him.
Sacraments are the principal and fundamental actions whereby Jesus Christ unceasingly bestows His Spirit on the faithful, thus making them the holy people who offer themselves, in Him and with Him, as an offering acceptable to the Father.
In the sacraments, Christ gives us His grace, which He purchased for us on the Cross, enabling us to become more like Him. In every sacrament it is Christ our High Priest Who brings His grace to us. The priests who administer the sacraments are His ordained representatives.
2. Sacraments are called actions of Christ because it is from Christ that they receive the power to make men holy.
To the Church belongs the power of administering the sacraments, and yet they are always to be referred to Christ, Who acts in and through them. It is from Christ that they receive their power. It is Christ Who baptizes. It is not so much a man who celebrates the Eucharist as Christ Himself; for it is Christ Who offers Himself in the Sacrifice of the Mass by the ministry of the priests. Priests offer the Holy Sacrifice of the Mass in the Person of Christ. The sacramental action is, in the first place, the action of Christ, and the priests of the Church are His instruments.