You know someone. He used to open his Bible every day, and he prayed with more feeling than you did. Now he finds the whole thing embarrassing, and he would rather you did not bring it up.

So what do you do with the promise that God keeps His people? He was one of them, or he looked exactly like one. Scripture answers with two men who failed in the same week.

Judas had been with Jesus for three years. He was not on the edge of the group; he was one of the twelve, sent out with the same commission as the rest, trusted with the money. Nobody at the table suspected him — when Jesus said that one of them would hand Him over, the others had no idea who He meant. And when he went, he did not come back.

Peter denied Christ three times that same night, in public, to a servant girl, swearing about it by the end. If you are ranking betrayals it is hard to say his was much better. He walked out and wept. By Friday morning, watching from a distance, you could not have told these two men apart. Both had turned on Him. Both were finished.

One of them came back. And the reason has nothing to do with their own efforts. Jesus told Peter beforehand exactly why he would return.

Luke 22:31–32 (NKJV)

And the Lord said, “Simon, Simon! Indeed, Satan has asked for you, that he may sift you as wheat. But I have prayed for you, that your faith should not fail; and when you have returned to Me, strengthen your brethren.”

Read what Jesus does not say. He does not say Peter will stand firm. He knows he will not — He says so four verses later. He says Peter's faith will not fail, which is a different thing, and He gives the ground for it: I have prayed for you. Then He says when you have returned, not if. The return was settled before the denial happened, and it was settled by Christ's prayer rather than by Peter's resolve, which had already been offered and was worthless.

So a true believer can fall further than anyone watching would think survivable, and still be held. That is what happened to Peter, and it is why nobody should write off a man who has gone quiet.

But Judas is also in the story, and he is the reason this question is painful. He did not fall and get up. He left. And the New Testament faces that plainly.

1 John 2:19 (NKJV)

They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.

John is not being dismissive of people he lost. He is explaining what their leaving showed. It did not take anything away from them — it made something visible that had been true the whole time. They had belonged to the church, sat in the meetings, used the same vocabulary, and they had never belonged to Christ. The going out was the revealing.

But notice who John is writing about: men who had already gone and stayed gone. He is not handing you a verdict to pronounce over someone still living. A man who is away today may be back in ten years, and his coming back will be God keeping him, not God changing His mind.

Someone will say this is too easy. Whenever a Christian keeps going, that proves God kept him. Whenever a Christian leaves, that proves he was never a Christian. Either way the doctrine wins, and no case could ever count against it.

That would be a fair complaint if Christians had invented the idea of a man who looks converted and is not. We did not. Jesus said it first, and He said it about people with far better credentials than those turning up on a Bible study night.

Matthew 7:22–23 (NKJV)

Many will say to Me in that day, “Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?” And then I will declare to them, “I never knew you; depart from Me, you who practice lawlessness!”

Everything hangs on two words. Never knew you. Not I knew you once and you drifted. Not you were Mine and you forfeited it. Jesus tells men who preached and cast out demons in His name that there had never been a relationship at all.

Which leaves the practical question: what to do about the person you are actually thinking of.

You do not know which man he is. That is not a failure of your discernment; nobody watching Peter that Thursday night knew either. So you do not write him off, and you do not pretend nothing has happened. You pray for him — which is what Jesus did for Peter, and it was the prayer, not the resolve, that brought him back. You keep the door open, because men do return, and their returning is not a second chance they earned but the same keeping power that never stopped.

And you leave the sorting where it belongs.

2 Timothy 2:19 (NKJV)

Nevertheless the solid foundation of God stands, having this seal: “The Lord knows those who are His,” and, “Let everyone who names the name of Christ depart from iniquity.”

Paul writes that in a letter about people who had abandoned the faith and taken others with them. He does not pretend it has not happened. He says the foundation is still standing, and that God has never once been confused about who is on it.