What happens to those who have died in Jesus when He comes?

Those who have died physically in Jesus are described as asleep, not without hope. Because Jesus died and rose again, God will bring them with Him when He comes. This is part of the revelation called being caught up, comforting believers concerning those who sleep in Christ.

Les teaches from 1 Thessalonians chapter 4 that the believer who has died physically is asleep, and the sorrow of those who have no hope is not to be the sorrow of the believer. He explains this is tied to the gospel: if we believe that Jesus died and rose again, even so them also who sleep in Christ, or in Jesus, who have died, God will bring with Him. Les also points out that in this portion Jesus and God are synonymous—the same God, the same Jesus. The passage is another extension of the revelation of the mystery he refers to as being caught up.

1 Thessalonians 4:14

For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.

Whose departed souls and spirits will God bring when Jesus returns?

When Jesus returns, God will bring the departed souls and spirits of believers only, not unbelievers. These believers' souls and spirits come from heaven to the atmosphere, where they will be reunited with their resurrected bodies. This occurs at the Lord's descent, and the dead in Christ rise first.