“[Soul sleep] teaches that when believers die they go into a state of unconscious existence, and the next thing that they are conscious of will be when Christ returns and raises them to eternal life…But when scripture represents death as “sleep” it is simply a metaphorical expression used to indicate that is only temporary for Christians, just as sleep is temporary. This is clearly seen, for example, when Jesus tells his disciples about the death of Lazarus. He says, ‘Our friend Lazarus has fallen asleep, but I go to awake him out of sleep’ (John 11:11). We should notice that Jesus does not here say, ‘The soul of Lazarus is sleeping,” nor, in fact, does any passage in Scripture say that the soul of a person is sleeping or unconscious (a statement that would be necessary to prove the doctrine of soul sleep). Rather Jesus simply says that Lazarus has fallen asleep. Then John explains, ‘Now Jesus had spoken of his death, but they thought that he meant taking rest in sleep. Then Jesus told them plainly, ‘Lazarus is dead’ (John 11:12-13).
“…The fact that Hebrews 12:1 says, ‘We are surrounded by so great a cloud of witnesses,’ just after an entire chapter spent on the discussion of the faith of Old Testament saints who had died (Heb. 11), and the fact that the author encourages us to run the race of life with perseverance because we are surrounded by this great cloud of witnesses, both suggest that those who have died and gone before have some awareness of what is going on in the earth. Scripture says very little about this, probably because it does not want us to speak to those who have died or to pray to them or to contact them in any way (note Saul’s great sin in this in 1 Samuel 28:7-25). Nonetheless, Hebrews 12:1-2 does give us this slight hint, probably as an encouragement to us to continue also to be faithful to God as were those who have died and gone to heaven before us. Similarly, at the end of Hebrews 12, the author tells us that when we worship we come into the presence of God in heaven, and we come not to ‘the spirits of just men who are sleeping in an unconscious state’ but ‘to innumerable angels in festal gathering, and to the spirits of just men made perfect, and to Jesus, the mediator of a new covenant’ (Heb. 12:22-24).
“Revelation 6:9-11 and 7:9-10 also clearly show the souls or spirits of those who have died and who have gone to heaven praying and worshiping, for they cry out with a loud voice, ‘O Sovereign Lord, holy and true, how long before you will judge and avenge our blood on those who dwell upon the earth?’ (Rev. 6:10) and they are seen ‘standing before the throne and before the Lamb, clothed in white robes, with palm branches in their hands, and crying out with a loud voice, ‘Salvation belongs to our God who sits upon the throne, and to the Lamb’ (Rev. 7:9-10)! All of these passages deny the doctrine of soul sleep, for they make it clear that the souls of believers experience conscious fellowship with God in heaven immediately upon death.”
(Wayne Grudem, “Death and the Intermediate State,” Systematic Theology, pp819-821, 2000)