Here Jesus is presenting Himself as the surety of His people before the Father. Having received the call and authority of the Father and being fitted with a body suited to the service of a redeemer, He is here entering into the work. With these words—“I sanctify myself”—did Jesus mean that He made Himself more holy for the purpose? No, that was impossible. Jesus’ sanctifying Himself must be understood as His presenting Himself as a voluntary offering, a holy unblemished sacrifice (as the Nazarite from the womb is consecrated, set apart, dedicated to the service to which the Father had called Him).
Notice that it is “for their sakes,” not for Himself. The priests under the law made their offerings, first for themselves, and then for the people. “But such an High Priest became us, who is holy, harmless, undefiled, separate from sinners … and who needed not daily, as those high priests, so to offer.” Pause over this view of Jesus and go to the mercy-seat, by faith, and behold Jesus, in His vesture dipped in blood, there sanctified, and there appearing in the presence of God for you. There you can plead the dedication of Jesus on your behalf.
There you can tell God that Jesus, that Holy One, whom the Father consecrated, and with an oath confirmed in His high priestly office forever, appears there for you. Tell God that your High Priest’s holiness and sacrifice was altogether holy, pure, without a spot, and both his Person, and His nature, and offering, clean as God’s own righteous law. Tell God these sacred, solemn truths. Go to God in prayer, and look to Jesus, and call to mind these sweet words—“And for their sakes I sanctify myself.” There you can beg, and pray, and wrestle with the bountiful Lord for suited strength and grace, so that you may be able to be separated from every thing but Jesus; and as your happiness was Christ’s end, so His glory may be your first and greatest object.