In John 15:1-8 Jesus taught as He did many times by using an analogy from things in the natural world. To teach His disciples about spiritual fruitfulness on this occasion, He compared Himself to a vine, and men to branches.
Jesus spoke of two different categories of men in this passage: those who abide or remain in Him, and those who do not. Those who abide in Christ are believers, and it is only because we “abide in the Vine” that we
are “branches” that can, and will indeed, bear fruit to the glory of God (John 15:8). In contrast, unbelievers do not abide in Christ, and therefore they are unable to bear fruit. In order for anyone to bear fruit to the glory of God, they must “abide in the Vine”, which is to say that they must be in union with Christ. In other words, they must be a believer.
A few verses later in John 15, Jesus said: “If you keep My commandments, you will abide in My love, just as I have kept My Father’s commandments and abide in His love.” (John 15:10). Here in John 15:10, and also in John 14:21-24, Jesus taught that men will demonstrate a genuine faith in Him by the fact that they walk in obedience to His commands.
The Apostle John also gave us this same teaching in 1 John 2:3-6 and 1 John 5:3-5. Believers will at times sin after they are saved, but the life of every believer will be characterized fundamentally by obedience and submission to God’s word, in contrast to those of the world whose lives will be characterized fundamentally by sin and self-seeking.
Therefore, by our obedience to God’s word we give evidence that we are genuine believers. And every genuine believer will bear fruit to the glory of God as a result of the fact that he “abides” in the Vine, in union with Christ. This fruit will be produced because by God’s grace we have been called to faith in Christ (1 Peter 1:1-2, and many others), and by God’s
power we abide or remain in Christ (Philippians 1:6, 1 Thessalonians 5:23- 24, 1 Peter 1:3-5).