John 17:19

"And for their sakes I sanctify Myself, that they also might be sanctified in the truth." What is, "I sanctify Myself"? "I offer to Thee a sacrifice." Now all sacrifices are called "holy," and those are specially called "holy things," which are laid up for God. For whereas of old in type the sanctification was by the sheep, but now it is not in type, but by the truth itself, He therefore saith, "That they may be sanctified in Thy truth." "For I both dedicate them to Thee, and make them an offering"; this He saith, either because their Head was being made so, or because they also were sacrificed; for, "Present," it saith, "your bodies a living sacrifice, holy"; and, "We were counted as sheep for the slaughter." And He maketh them; without death, a sacrifice and offering; for that He alluded to His own sacrifice, when He said, "I sanctify," is clear from what follows.

(Tr. cviii) It is manifest by this, that He is still speaking of the Apostles; for the very word Apostle means in the Greek, sent. But since they are His members, in that He is the Head of the Church, He says, And for their sakes I sanctify Myself; i. e. I in Myself sanctify them, since they are Myself. And to make it more clear that this was His meaning, He adds, That they also might be sanctified through the truth, i. e. in Me; inasmuch as the Word is truth, in which the Son of man was sanctified from the time that the Word was made flesh. For then He sanctified Himself in Himself, i. e. Himself as man, in Himself as the Word: the Word and man being one Christ. But of His members it is that He saith, And for their sakes I sanctify Myself, i. e. them in Me, since in Me both they and I are. That they also might be sanctified in truth: they also, i. e. even as Myself; and in the truth, i. e. Myself.

But since, on the ground that the Mediator between God and men, the man Christ Jesus, has become Head of the Church, they are His members; therefore He says in the words that follow, "And for their sakes I sanctify myself." For what means He by the words, "And for their sakes I sanctify myself," but I sanctify them in myself, since they also are [part of] myself? For those of whom He so speaks are, as I have said, His members; and the head and body are one Christ, as the apostle teaches when he says of the seed of Abraham, "And if ye be Christ's, then are ye Abraham's seed," after having said before, "He saith not, And to seeds, as in many, but as in one, And to thy seed, which is Christ." If, then, the seed of Abraham is Christ, what else is declared to those to whom he says, "Then are ye Abraham's seed," but then are ye Christ? Of the same character is what this very apostle said in another place: "Now I rejoice in my sufferings for you, and fill up that which is lacking of the afflictions of Christ in my flesh." He said not, of my afflictions, but "of Christ's;" for he was a member of Christ, and in his persecutions, such as it behoved Christ to suffer in the whole of His body, he also was filling up his own share of His afflictions. And to be assured of the certainty of this in the present passage, give heed to what follows. For after saying, "And for their sakes I sanctify myself," to let us understand that He thereby meant that He would sanctify them in Himself, He immediately added, "That they also may be sanctified in the truth." And what else is this but in me, in accordance with the fact that the truth is that Word in the beginning which is God? In whom also the Son of man was Himself sanctified from the beginning of His creation, when the Word was made flesh, for the Word and the man became one person. Then accordingly He sanctified Himself in Himself, that is, Himself the man in Himself the Word; for the Word and the man is one Christ, who sanctifies the manhood in the Word. But in behalf of His members He says, "And for their sakes I,"-that is, that the benefit may be also theirs, for they too are [included in the] I, just as it benefited me in myself, because I am man apart from them-" I sanctify myself," that is, I sanctify them as if it were my own self in me, since in me they also are I. "That they also may be sanctified in the truth." For what else mean the words "they also" but ["they"] in the same way as I; "in the truth," and that "truth" am I?