“sanctify myself” = Jesus completely set Himself apart to God (Eph 5:2, Heb 7:27, 9:14). By saying (John 12:28, Matt 26:42, Luke 23:46) Jesus also sanctified Himself. How?

Ephesians 5:2  and live a life of love, just as Christ loved us and gave himself up for us as a fragrant offering and sacrifice to God.

Hebrews 7:27  Unlike the other high priests, he does not need to offer sacrifices day after day, first for his own sins, and then for the sins of the people. He sacrificed for their sins once for all when he offered himself.

Hebrews 9:14  How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God!

John 12:28  Father, glorify your name!” Then a voice came from heaven, “I have glorified it, and will glorify it again.”

Matthew 26:42  He went away a second time and prayed, “My Father, if it is not possible for this cup to be taken away unless I drink it, may your will be done.”

Luke 23:46  Jesus called out with a loud voice, “Father, into your hands I commit my spirit.” When he had said this, he breathed his last.

Luthi states, “He serves as Mediator between Heaven and earth. He sanctifies Himself by placing Himself completely at His Father’s service and saying, ‘Not my will, but thine, be done.’ His path of duty leads through the Cross and the grave to Resurrection, and up to the right hand of the Father, from whence He shall come again. The absolute, voluntary filial obedience is the secret of Christ’s self-sanctification. That is what He means when He stands alone before the Father here and vows to Him, ‘I sanctify myself.’”

The sacrifice of Jesus purchased the sanctification of the church (Eph 5:25-26). It is the ultimate consecration of Jesus to His sacrifice on the cross that enables the consecration — setting apart — of the children of God. As the priest and Levites in the Old Testament were consecrated by the shedding of blood so are we, but with a much better blood. Therefore it only follows that our setting apart to the work God has called us to do is much better than that of the priests and Levites.

Ephesians 5:25-26  Husbands, love your wives, just as Christ loved the church and gave himself up for her  to make her holy, cleansing her by the washing with water through the word,

What has God called you to do? Is He even now preparing you for a work? What are you going to say when He says, “Go” and in whose power will you go if you do?