The Proof is in the Pudding
If the proof of the pudding is in the eating, then the proof of the Christian is in the living. In this verse, Jesus is saying, "If you truly follow me, you'll live like it." The greatest test of faith is, and will continue to be, time. The word "abide" means to remain, or stay put. Hebrews 3:14 (NLT) says, "For if we are faithful to the end, trusting God just as firmly as when we first believed, we will share in all that belongs to Christ."
The question is, will you remain in the faith, or will you walk away? For some, time reveals an emotional commitment made without counting the cost. As soon as things get difficult, or don't turn out like they thought it would, they abandon ship. But true faith leads to new life and reformation. It is always faith that saves alone, but faith that saves is never alone. Where God has done a work, it starts inside and works its way out. That's not to say that a believer will never struggle, fall, or backslide. It means that when they do—though they might stay there for days, weeks, or months—they will get back up. Sin causes slavery and a need for salvation, but once that salvation has truly taken place, there will be a radical difference in the way you live. Those born of God don't become practiced in sin, getting better and better at it. Instead, they practice righteousness, abiding in Christ, bearing fruit day by day as sin's grip on their life becomes less and less. "And a slave does not abide in the house forever, but a son abides forever. Therefore, if the Son makes you free, you shall be free indeed."
Remember: Faith alone saves, but faith that saves is never alone.
(Excerpt from 21 Days in the Book of John by Levi Lusko and Fresh Life Church)