Neither can you bear fruit unless you remain in me. This is not the inorganic growth of external accretion, like the growth of an alum crystal in an alum solution; it is organic growth, internal growth, driven by the pulsating life of the vine in the branch, and only this kind of growth produces fruit. The imagery of the vine is stretched a little when the ‘branches’ are given the responsibility to remain in the vine, but the point is clear: continuous dependence on the vine, constant reliance upon him, persistent spiritual imbibing of his life–this is the sine qua non of spiritual fruitfulness. The Christian or Christian organization that expands by external accretion, that merely apes Christian conduct and witness, but is not impelled by life within, brings forth dead crystals, not fruit.

The Gospel according to John (The Pillar New Testament Commentary (PNTC)) . Eerdmans Publishing Co – A. Kindle Edition.