A.T. Robertson Commentary John 17:19

"And for their sakes I sanctify myself, that they themselves also may be sanctified in truth." — John 17:19 (ASV)

I sanctify myself (εγω αγιαζω εμαυτον). To his holy ministry to which the Father "sanctified" (ηγιασεν) him (John 10:36).

That they themselves also may be sanctified in truth (ινα ωσιν κα αυτο ηγιασμενο εν αληθεια). Purpose clause with ινα and the periphrastic perfect passive subjunctive of αγιαζω (that they may remain sanctified). The act of Christ helps us, but by no means takes the place of personal consecration on the part of the believer. This high and holy prayer and act of Christ should shame any one who uses the livery of heaven to serve the devil in as does, alas, sometimes happen (2 Corinthians 11:13–15).