Jamieson, Fausset & Brown

Every branch in me that beareth not fruit . . . every branch that beareth fruit--As in a fruit tree, some branches may be fruitful, others quite barren, according as there is a vital connection between the branch and the stock, or no vital connection; so the disciples of Christ may be spiritually fruitful or the reverse, according as they are vitally and spiritually connected with Christ, or but externally and mechanically attached to Him. The fruitless He "taketh away" (see on Joh 15:6); the fruitful He "purgeth" (cleanseth, pruneth)--stripping it, as the husbandman does, of what is rank (Mar 4:19), "that it may bring forth more fruit"; a process often painful, but no less needful and beneficial than in the natural husbandry.