15 "“I am the true vine, and my Father is the vine dresser. 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
Before continuing with our Lord's teaching in this chapter, it will be useful to look at the last words of 14:31, 'Arise, let us go hence'. Some have thought that Jesus and the disciples must have left the Upper Room at this point, and that what follows was spoken elsewhere. But it is not necessary to make this assumption. C.H. Dodd points out that the Greek verb translated 'let us go' implies, in normal Greek usage, 'let us go to meet the advancing enemy' and that the sentence should be construed with what is said in 30 about the prince of this world having nothing in Jesus. No physical movement is therefore indicated here, simply our Lord's spiritual determination to go forth to challenge the prince of this world, in obedience to the Father's will. 'Let us march to meet him', Jesus means. And, in this connection, the context here gives the words a remarkably graphic emphasis, for it is only as we are in fellowship with the Father and the Son (this has been the subject matter of much of chapter 14) that we can engage in the Lord's service. This also means that obedience is the touchstone of effectiveness for, as we have seen, obedience is integrally related not only to the possibility of fellowship with the Father and the Son, but also to the presence and work of the Spirit and to the life of prayer. Satan may well tremble when he is confronted with an utterly obedient disciple, for this means that all the power of the Godhead is lined up against him.