1 “I am the true vine, and my Father is the vinedresser. 2 Every branch in me that does not bear fruit he takes away, and every branch that does bear fruit he prunes, that it may bear more fruit. 3 Already you are clean because of the word that I have spoken to you. 4 Abide in me, and I in you. As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me. 5 I am the vine; you are the branches. Whoever abides in me and I in him, he it is that bears much fruit, for apart from me you can do nothing. 6 If anyone does not abide in me he is thrown away like a branch and withers; and the branches are gathered, thrown into the fire, and burned.” – John 15:1-6
What Christ put forward in the parable of the sower He now puts forth in a didactic analogy. Christ begins by equating Himself with Israel through vineyard imagery (Isa 5; etc.). As the “true vine,” Christ relates to those listening to His teaching as the source of their life. He is the only faithful Israel and all of Israel's covenant promises will come through Him. The new bride and body of Christ is not a replacement to the old covenant Israel. Christ is the fulfillment and the church is integrated through becoming one flesh in marriage.
Time does not permit to relate the full breadth of John’s “abide in me” theology but here it is takes a pronounced center stage. As Christ is the source it follows that the church is not self-sustaining. There is no salvation or justification apart from union with Jesus Christ. In this vein, Christ affirms that every branch "in Him" is “clean” (G2513). This word, often translated “pure,” is used in a baptismal way in the book of Hebrews (Heb 10:22). Of these “clean” branches only the fruitful avoid the flames. Christ is not speaking generically about believers and non-believers. He is drawing an explicit covenantal line between those who are in fact "in Him." This would seem to support the thesis of Christ’s parable of the soils. It also brings to the forefront the major theme of John's writing: abiding in Christ. Abiding in the true vine is essential for those who have once been cleaned by the word of God. This language hints of Peter's teaching in 2 Peter 1:9.
This cleansing of the word that Christ attributes to all branches, even those destroyed, should bring to life Paul’s teaching in Ephesians (Eph 5:26) and Titus (Titus 3:5). These branches that are destroyed are legitimately, and historically, “in Christ” at some point. These branches that are destroyed were certainly cleansed. The prophetic imagery of Ezekiel, Isaiah, and Jeremiah that concerns washing and purity leap into fulfillment in through the new covenant founded in Jesus. Christ is speaking to a new covenant community that will have heard His word and believed Him (John 8:31). Christ challenges them to “abide” (John 8:31), much like He does here in John 15, only to have them disbelieve when He speaks great truth (John 8:45-47).