17 Besides this power over the real Body of Christ, the priest has received other powers, august and sublime, over His Mystical Body of Christ, a doctrine so dear to St. Paul; this beautiful doctrine that shows us the Person of the Word-made-Flesh in union with all His brethren. For from Him to them comes a supernatural influence, so that they, with Him as Head, form a single Body of which they are the members. Now a priest is the appointed "dispenser of the mysteries of God," for the benefit of the members of the mystical Body of Christ; since he is the ordinary minister of nearly all the Sacraments, - those channels through which the grace of the Savior flows for the good of humanity. The Christian, at almost every important stage of his mortal career, finds at his side the priest with power received from God, in the act of communicating or increasing that grace which is the supernatural life of his soul.
Source: Ad Catholici Sacerdotii (Vatican.va)