John 17:18

Jesus next explained the purpose of the sanctification that He requested for His disciples. He had sent them into the world with a mission (cf. John 13:20; John 15:26-27; John 20:21). Similarly the Father had sent the Son into the world with a mission (John 10:36). In both cases sanctification was essential for the success of the mission.

Comparison with John 17:20 shows that in John 17:6-19 Jesus was praying specifically for the Eleven. However, we should not regard what He requested for the Eleven as restricted to them exclusively. The change that takes place in John 17:20 is not from one group of believers to another as though they were in separate containers. It is rather a broadening of the field from the Eleven to those that would follow them. Thus it is understandable that when Jesus prayed for the Eleven He would pray for some things that not only they but their successors would need. Clearly all subsequent believers would need sanctifying by God’s Word so they could achieve their mission, as the Eleven did.