Read John 15.
This section, John 13-16 records the final extended teaching Jesus gave to his disciples before his death. Here in chapter 15, Jesus told the disciples that they would bear fruit for him (vv. 1-17), be persecuted because of him (vv. 18-25), and testify for him (vv. 26-27). Each of these is demanding. However, Jesus does not command any of them. Instead, he describes them as products of being “in him.” If disciples “remain in me,” Jesus said, “you will bear much fruit” (v. 5b). Likewise, the world would persecute them “because of my name” (v. 21b) and they would testify “for you have been with me from the beginning.” So Jesus does not command us to do these things. Rather, his command is “remain in me” and all these things will flow out of that.
So what does remaining in Jesus mean? It means to keep believing in him, to maintain our faith in him and continue following him as Lord. This is another way of describing the doctrine of the perseverance of the saints. That doctrine teaches that all those who are genuinely saved will continue from the time of their salvation until the end of their lives in faith and good works. Anyone who does not “remain in Jesus” then, goes to hell (v. 6). That person’s attachment to Jesus was superficial not genuine.
If you belong to Jesus, then, it will show in your life. Not every branch has the same level of fruitfulness but all the branches bear some fruit. Do you see the evidence of Christ’s work in your life? is there spiritual growth in your life so that you know Christ better and trust in him more now than in the past? This is a fulfillment of Christ’s promise in this passage. We can’t produce spiritual fruit on our own because “apart from me you can do nothing” (v. 5b). Cultivate your connection to Christ by faith, then, and God will work on your life (“he prunes” v. 2) and through your life to make fruit through you for his glory.