19 And I consecrate Myself so that they also might be consecrated in truth.
We have already seen that to be consecrated is to be set apart, which is also to be holy. The word is specifically about being devoted to something in particular. This does not mean that all other things are unholy, but that consecration is being given over to a particular task or mission.
In His praying Jesus was consecrating Himself in order that His disciples might be consecrated in the truth. We must remember that it was the Passover time, and many sacrifices would have been made to celebrate the Passover. Jesus was about to become the greatest Passover sacrifice as He went to the cross to pay the price of our sin. In this He was consecrating Himself in sacrifice for His disciples and, more generally, for us all.
The consecration that Jesus was making was one that only He could make. By doing this He was consecrating Himself to be our great High Priest. The writer to the Hebrews put it this way:
That is why we have a great High Priest who has gone to heaven, Jesus the Son of God. Let us cling to Him and never stop trusting Him – Hebrews 4.14 (NLT).
Jesus was totally devoted to the mission that the Father had given to Him to do – saving sinners.
This was a mission in which He was involving His disciples, and all who follow Him. This does not mean that the disciples could assist Him in His consecrated work on the cross, but it does mean that they were to be consecrated as the proclaimers of the message of the cross.
We are also consecrated into this task, since we are all called by Jesus to be His witnesses in the location in which He has placed us. We have all been called and set apart (consecrated) by Jesus, and filled with the Holy Spirit, so that we are powerfully enabled to devote ourselves to serving Him.