Does the Scriptures ever speak of souls sleeping anywhere?
A common idiom for death is sleep.
"But man dies and is laid away; indeed he breathes his last and where is he? As water disappears from the sea, and a river becomes parched and dries up, so man lies down and does not rise. Till the heavens are no more, they will not awake nor be roused from their sleep. Oh, that You would hide me in the grave, that You would conceal me until Your wrath is past, that You would appoint me a set time, and remember me! If a man dies, shall he live again? All the days of my hard service I will wait, till my change comes. You shall call, and I will answer You; You shall desire the work of Your hands" (Job 14:10-15).
Job understood that men die, but they are not permanently dead. Like a man who goes to sleep, they will be awakened again, but it won't be anytime soon. The Lord will not call those who have died to awake until the heavens have disappeared. Job looked forwarded to the time he would answer the call of God. This is why death is sometimes called "sleep." It is to emphasize that it is not a permanent state; death does not last forever.
"Otherwise it will happen, when my lord the king rests with his fathers, that I and my son Solomon will be counted as offenders" (I Kings 1:21). The word given as "rests" here is literally "sleeps."
"And many of those who sleep in the dust of the earth shall awake, some to everlasting life, some to shame and everlasting contempt" (Daniel 12:2).
"Then, behold, the veil of the temple was torn in two from top to bottom; and the earth quaked, and the rocks were split, and the graves were opened; and many bodies of the saints who had fallen asleep were raised; and coming out of the graves after His resurrection, they went into the holy city and appeared to many" (Matthew 27:51-53).
"These things He said, and after that He said to them, "Our friend Lazarus sleeps, but I go that I may wake him up." Then His disciples said, "Lord, if he sleeps he will get well." However, Jesus spoke of his death, but they thought that He was speaking about taking rest in sleep. Then Jesus said to them plainly, "Lazarus is dead"" (John 11:11-14).
"Then he knelt down and cried out with a loud voice, "Lord, do not charge them with this sin." And when he had said this, he fell asleep" (Acts 7:60). To say that Stephen died would have been too final. It would make it appear that those that murdered him had triumphed. By saying that he fell asleep emphasizes that the death was only temporary.
"For David, after he had served his own generation by the will of God, fell asleep, was buried with his fathers, and saw corruption" (Acts 13:36).
"After that He was seen by over five hundred brethren at once, of whom the greater part remain to the present, but some have fallen asleep" (I Corinthians 15:6).
"But now Christ is risen from the dead, and has become the firstfruits of those who have fallen asleep. For since by man came death, by Man also came the resurrection of the dead. For as in Adam all die, even so in Christ all shall be made alive" (I Corinthians 15:20-22).
"Behold, I tell you a mystery: We shall not all sleep, but we shall all be changed" (I Corinthians 15:51). By this Paul is stating that when end comes, there will be Christians still alive (not all will sleep). But whether we are alive or dead at the glorious coming of our Lord, we will all be changed.
"But I do not want you to be ignorant, brethren, concerning those who have fallen asleep, lest you sorrow as others who have no hope. For if we believe that Jesus died and rose again, even so God will bring with Him those who sleep in Jesus. 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 will by no means precede those who are asleep. For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. 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. Therefore comfort one another with these words" (I Thessalonians 4:13-18).
"For God did not appoint us to wrath, but to obtain salvation through our Lord Jesus Christ, who died for us, that whether we wake or sleep, we should live together with Him. Therefore comfort each other and edify one another, just as you also are doing" (I Thessalonians 5:9-11).
"Knowing this first: that scoffers will come in the last days, walking according to their own lusts, and saying, "Where is the promise of His coming? For since the fathers fell asleep, all things continue as they were from the beginning of creation."" (I Peter 3:3-4).