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. [John 15:6]
If we read this a certain way, it sounds like the branches are cast into the fire as soon as they are cut off. Jesus does not say that the branch gets a chance to reattach.
But let's look at the sequence of events: The branch was cut off and thrown away, it withered, it was gathered up, and finally it was thrown into the fire. This does leave at least one step in between the cutting off and the casting into flames. There is a period where it lies on the ground withering.
Now, what if the branch was picked up before it finished drying out, and was nourished and reattached to the vine? Do the scriptures support such a possibility?
If some of the branches have been broken off, and you, though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, do not boast over those branches. If you do, consider this: You do not support the root, but the root supports you. You will say then, "Branches were broken off so that I could be grafted in." Granted. But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but be afraid. For if God did not spare the natural branches, he will not spare you either.Consider therefore the kindness and sternness of God: sternness to those who fell, but kindness to you, provided that you continue in his kindness. Otherwise, you also will be cut off. And if they do not persist in unbelief, they will be grafted in, for God is able to graft them in again. After all, if you were cut out of an olive tree that is wild by nature, and contrary to nature were grafted into a cultivated olive tree, how much more readily will these, the natural branches, be grafted into their own olive tree! [Romans 11:17-24]
I bring this up because it uses a similar analogy of branches, but in this case it shows that branches can be removed and reattached. The problem is, however, that this verse is being applied to groups of people (Jews and Gentiles), thus it might not necessarily apply to individuals (e.g. if faith disappeared among Gentiles, the Jews would once again be grafted in). However, in my reading he is actually applying it to both. Yes, the Jews lost their place, but this happened “because of unbelief.” This is an individual level lack of faith. The Jews certainly did not reject Christ “as a people,” for the majority of early converts were Jews, including the writer of this verse.
Still, I will move on to an example that does not have the additional complexity of speaking about whole groups of people.
My brothers, if one of you should wander from the truth and someone should bring him back, remember this: Whoever turns a sinner from the error of his way will save him from death and cover over a multitude of sins. [James 5:19-20]
First, notice that James is speaking to his “brothers,” meaning fellow Christians. Second, notice that they “wander from the truth.” What would it mean for a “brother” to “wander from the truth?” It means that he was a saved person, abiding in Christ, but he abandoned the faith. But then it goes on to say that someone could “bring him back” and “save him from death.”
Thus, the scriptures do support the idea that one can be saved, but then lose his salvation, and finally be brought back to salvation. A removed branch can be reattached.