What does John 17:19 mean?

Jesus has used the term "sanctify," from the Greek hagiazō, in reference to His followers being "set apart" from the world, even as they remain in it (John 17:16–17). This is part of the High Priestly Prayer in which Christ asks God the Father to maintain the faith of those who will follow Jesus (John 17:1–11). Those who have accepted the message Jesus proclaimed—the "word" of God—have been saved and made clean through that faith (John 15:3; 17:8).

The ESV translates the same term—hagiazō—as "consecrate" here, while most other translations maintain the English word "sanctify." There is a difference, however, in how Jesus now "consecrates / sanctifies" Himself, and the way in which His followers are set apart from the world. The separation about which Jesus now prays refers to Him being taken by His enemies to be killed (John 13:36).

An integral part of the gospel is that the Messiah will suffer and die for the sins of mankind (Mark 8:31; John 12:31–33; 1 Corinthians 15:3–5). This is a role only Jesus can fulfill (Matthew 26:53–54; John 3:16–18). While the truths of God can be spoken by others (John 14:26), and even some of the works Jesus did can be repeated by others (John 14:12), only the sinless Son of Man can become the means by which mankind is saved (John 14:6; Acts 4:12).

Appropriately, Jesus will pivot after this statement into an explicit prayer for all Christian believers. To this point, He has prayed for Himself (John 17:1–5) and most specifically for His closest followers (John 17:6–18). The broad strokes of His prayer for the apostles extend to other believers, but what comes next is directly addressed to the experience of those who come to faith because of the Apostles' efforts (John 17:20).