"The best explanation, however, is that it is referring to professing Christians who outwardly have no living connection and therefore cannot bear the fruit that can be expected of a fruitful branch." (Walvoord, p. 428, Every Prophecy of the Bible)
You are already clean because of the word I have spoken to you. Remain in me, and I will remain in you. No branch can bear fruit by itself; it must remain in the vine. Neither can you bear fruit unless you remain in me. "I am the vine; you are the branches. If a man remains in me and I in him, he will bear much fruit; apart from me you can do nothing. If anyone does not remain in me, he is like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned.
A few notes of interest...
Jesus' audience is "clean" because of the word He had spoken to them. Their Salvation was on credit.
Jesus stress 4x that Christians can do nothing without Him living within. Think that's important to know?
- No branch can bear fruit by itself
- Neither can you bear fruit unless you remain in me.
- apart from me you can do nothing.
- If anyone does not remain in me, he is like a branch that is thrown away and withers;
- If you remain in me and my words remain in you, ask whatever you wish, and it will be given you. This is to my Father's glory, that you bear much fruit, showing yourselves to be my disciples.