An older gentleman who likes to talk with me about spiritual things whenever he sees me often likes to talk about the afterlife. He raised the subject of "soul sleep" with me, and sort of tried to defend that position. This is another one of those things that isn't an "essential" doctrine, as a belief one way or another doesn't change one's eternal destiny, but it does make me wonder how one arrives at such a conclusion based on what the Bible says.

Anyone who trusts in Jesus Christ for their salvation and then dies will go immediately to heaven to be in the glorious presence of the Almighty God. A decomposing shell of a body that once housed a soul may be in the grave, but their soul and spirit ( what makes us real ) goes into the abode of Jesus Christ. When the Lord returns for His church, the "dead in Christ" will return with Him, and the bodies they left behind will be glorified, raised and reunited with their souls. Likewise, the living bodies of those trusting in Jesus that are still alive on the earth when He returns are transformed into the glorified state of their resurrected counterparts.

There isn't an intermediate time or place where the soul "sleeps." Instead, the saved are in heaven with the Lord, in His wonderful presence, being shown His love and mercy while they praise and worship Him. Philippians 1:21-23 Paul shows this to be true;

21 For to me, to live is Christ, and to die is gain. 22 But if I live on in the flesh, this will mean fruit from my labor; yet what I shall choose I cannot tell. 23 For I am hard pressed between the two, having a desire to depart and be with Christ, which is far better.Most likely chained daily to a Roman soldier, awaiting his trial and faced with the hard reality that he would be put to death, Paul nevertheless had supreme confidence that he would be delivered from physical death, and also remained steadfast in his conviction that if he died, he would be much better off because he knew he would be with the Lord. That sort of statement coming from this amazing man of God doesn't advance a doctrine of "soul sleep."

Look at 2nd Corinthians 5:6-8: "6 So we are always confident, knowing that while we are at home in the body we are absent from the Lord. 7 For we walk by faith, not by sight. 8 We are confident, yes, well pleased rather to be absent from the body and to be present with the Lord."
Paul's words illustrate that the body is just a temporary home for our souls, and that we should be much happier to be with the Lord, our real home.

1 Thessalonians 4:13-18. "13 But we do not want you to be uninformed, brethren, about those who are asleep, that you may not grieve, as do the rest who have no hope. 14 For if we believe that Jesus died and rose again, even so God will bring with Him those who have fallen asleep in Jesus. 15 For this we say to you by the word of the Lord, that we who are alive, and remain until the coming of the Lord, shall not precede those who have fallen asleep. 16 For the Lord Himself will descend from heaven with a shout, with the voice of the archangel, and with the trumpet of God; and the dead in Christ shall rise first. 17 Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air, and thus we shall always be with the Lord. 18
Therefore comfort one another with these words."

The way that being "asleep" is used in this passage is metaphorical. For us as believers, death has a resemblance to sleep, so a metaphorical comparison is being made. But it works that way only if we believe what the New Testament tells us is true. Paul's use of the language is meant to suggest what death is like, but only as understood in the light of the whole of Scripture.

A person who sleeps doesn't stop being a person while their body sleeps. It's the same way when a believer dies. The grave is just a storage place for the body.