Jesus’s words have a meandering quality at first glance. Though it seems we have now, starting with 15:18, left the fruitfulness discussion, there is a direct line running from 15:11 and 15:16 to 16:24. The disciples fruitful prayer and their abundant joy (a fruit of the Spirit according to Paul, to stretch the exegesis a bit), are still at issue as Jesus takes up the topic of the disciples’ coming hardship.
From 15:18 (“if the world hates you”) to 16:33 (“you will have tribulation”), that hardship is the point, which helps us put all the other bits in perspective. It is with good reason that the Spirit is called Advocate, Helper, or Comforter in this passage. His ministry is variously described: to testify (15:26); to convict (16:8–11), to guide into truth (16:13), and to glorify Jesus (16:14). But this all hangs tightly together around the logic of his advocate-comforter function. The disciples’ hardship will be on account of Jesus’s name (15:21), that is, on account of their testimony about him (15:27). If they keep their mouths shut, there won’t be a problem. If they don’t, the Spirit will be with them.
This testimony is actually an echo of, or better yet, symphonic with the Spirit’s testimony (15:26). This seems to be the first statement of an idea that will come to full expression in chapter 17. Jesus is the one sent by the Father (15:21; 16:5) and the Spirit is the one sent by Jesus (15:26; 16:7). Yet, in the same way, the disciples are sent to testify. In fact, if the Spirit’s testimony is that which convicts the world, guides the disciples, and glorifies Jesus—and I believe it is—then the disciples’ testimony may serve the same purposes! Their witness will convict the world, guide other disciples, and glorify Jesus, though always in symphony with the work of the Spirit. The “and you also” of 15:27 is just as significant as the “just as . . . I also” of 17:18 (and 20:21), which has been tremendously important in the last sixty years among theologians of mission.
As the Father sent Jesus, so Jesus sends the Spirit and the disciples. The disciples will receive all that the Spirit possesses, which he received from Jesus, and which Jesus received from the Father (16:13-14). The world did not know the Father, so they hated Jesus; as they hated Jesus and did not know him, so they will hate the disciples. You can see the sense of it. There is deep relatedness, which will be expressed even more completely in chapter 17. That relatedness is the essence of the joy (16:24) and peace (16:33) that Jesus promises in the midst of their persecution and the sorrow of his absence. It is actually to the disciples’ benefit that he leave them, because it is better that the Spirit should be with them. The Spirit is who will accompany them in their witness and complete the relational dynamic that Jesus envisions for them.
Lastly, returning to the line running through 15 and 16, there are various statements about why Jesus is telling them “these things.”
15:11 I have said these things to you so that my joy may be in you, and that your joy may be complete.
16:4 I have said these things to you so that when their hour comes you may remember that I told you about them.
16:33 I have said these things to you so that in me you may have peace.
Of course, we must decide the antecedent of “these things” in each case, but I find it likely that the cadence of the phrasing brings all three of them into synonymy regarding everything that he has said about their fruit, their witness, their prayer, their sorrow, and their tribulation. Joy, remembrance, and peace are the sustenance of the disciples’ prayerful, fruitful testimony in symphony with the Spirit amid sorrow and hardship.