In Christ's passion, we find more than His substitutionary death. We find Him praying for us. Of course, the attention during the celebration of this event is properly placed on His death and resurrection, for without it there is no salvation. We cannot be Christians without God justifying us by Christ's blood. But if we miss Christ praying for us, we miss out on assurance throughout our salvation.
The first thing to note when we come to John 17 is something not explicit in the text. It is implied. In Christ's prayer, both His dependence on the Father and His love for His own are abundantly clear. You can almost hear through the pages the passion with which He prays. It is no light, obligatory prayer; there is both depth and weight to each word spoken.
The first assurance Christians find in this prayer is that Christ's blood actually atones for their sin. Although Christ had not yet died, His prayer reveals He understood the implication of the event that would soon take place. He prays, "Father, the hour has come; glorify your Son that the Son may glorify you, since you have given him authority over all flesh, to give eternal life to all whom you have given him." Earlier, John records a similar statement from Christ,
"All that the Father gives me will come to me, and whoever comes to me I will never cast out" (John 6:37)
Jesus speaks and prays with confidence that those the Father had freely and mercifully chosen before creation would certainly come to Him. Not only would they come, but they would also be saved. His blood would certainly atone for their sins.
To incorporate this into our practical theology, we cannot say that Jesus died for every sinner. He only died for the sinners who come to Him, trusting in Him for salvation. In both His teaching and prayer, it is clear that Jesus only expects His blood to save those who come to Him. So this is our confidence, not that Jesus died for a possible salvation for everyone but that His death surely saves those who come to Him.
As Jesus continues to pray, His attention is shifted to the disciples with Him. They were to become apostles, meaning they would carry His authority throughout the world in a way that the rest of Christ's followers – both the ones present and the ones to come – would not.
I have manifested your name to the people whom you gave me out of the world. Yours they were, and you gave them to me, and they have kept your word. (John 17:6)
Jesus makes two things clear: these men are there because of God, and they will stay there because of His Word. These are two assurance-producing truths. How can these disciples fear anything that would come against them? It wasn’t until the Holy Spirit bore witness of this in their hearts that they increased in boldness, but nonetheless these were solid foundational truths for their ministries. From these, they would not depart.
The apostles did not move their feet from the foundation of God's Word. It was their only hope, their only desire, and their great joy. Through the Word, they were made to look different than the world (v 17), but they were also, by that same Word, sent out into the world (v 18). They walked the earth like aliens in a foreign nation.
I do not ask for these only, but also for those who will believe in me through their word, that they may all be one, just as you, Father, are in me, and I in you, that they also may be in us, so that the world may believe that you have sent me. (John 17:20-21)
Jesus turns His focus toward the Christians who would come from the apostles. His prayer for unity is a prayer for their union with Himself; that the posterity of Adam, formerly alienated from God, would be reunited with God. "This is assuredly a remarkable ground of confidence," John Calvin writes, "for if we believe in Christ through the doctrine of the Gospel, we ought to entertain no doubt that we are already gathered with the apostles into his faithful protection, so that not one of us shall perish."
Herein is the unity Christ prays for; that we might be united to God with all those united in Christ. Our differences are not grounds to question if God heard Christ's prayer at this point. They rather make it clear that Christ was heard, for who would think that throughout the whole world – every tribe, nation, and tongue; individually different – could come a united people? Yet, here we are today unified in Christ.
Christ’s prayer is for our assurance that what God has set out to do in saving us in Christ, He will complete. Again, Calvin gives us a helpful description of this prayer, “This prayer of Christ is a safe harbour, and whoever retreats into it is safe from all danger of shipwreck; for it is as if Christ had solemnly sworn that he will devote his care and diligence to our salvation.”
Without Christ’s death, we cannot be saved. And without Christ’s prayer, we would lack assurance. When you doubt Christ, hear Him pray for you, for therein will you find your confidence in Him again. He cares for you more than you can know, so be assured of the effective work of Christ in your hearts.