Lets look at what YHWH revealed to the Old Testament writers about death and life. Obviously God can give more light in the New Testament but it cannot contradict what he has given already as truth in the Old.
6:4 Return, O LORD, deliver
my soul: oh save me for thy mercies' sake.
6:5 For in death there is no remembrance of thee: in the grave (Sheol) who shall give thee thanks?
Psalms 6:4-5
Note here the writer asks YHWH to deliver his
SOUL. Why? Because he thought he was near to death. Why would he be concerned about his soul dying if it was immortal?
Then he asks in
Sheol/Hades who will give you thanks? The Psalms were looked at by Jesus as inspired of YHWH. They were not just nice songs but rather were teachings given to believers.
So Sheol/Hades was a place where no one was giving thanks to YHWH. Had the righteous been alive there they would have both remembered YHWH and been giving him thanks.
115:17 The dead praise not the LORD, neither any that go down into
silence.
Psalms 115:17
Here we have it confirmed that the dead do not praise the Lord. Why? Because in Sheol/Hades all there is
IS SILENCE. It is a place where the dead sleep metaphorically speaking. Nothing happens there.
9:10 Whatsoever thy hand findeth to do, do it with thy might; for there is no work, nor device, nor knowledge, nor wisdom, in the grave, (Sheol) whither thou goest.
Ecclesiastes 9:10
Here again the Spirit is revealing truth. If this had never been taught in the Old Testament scripture then we could be taught something else in the New. Yet
THIS is what YHWH wanted men to believe. This is what his inspired vessels taught.
If there is no device, no wisdom, no work, or no knowledge in
Sheol/Hades then obviously there are not millions of people there some praising YHWH and others burning in fire.
The great prophet Isaiah records for us the words of Hezekiah the great King who turned Israel back to YHWH.
38:18
For the grave (Sheol/Hades) cannot praise thee, death can not celebrate thee: they that go down into the pit cannot hope for thy truth.
38:19
The living, the living, he shall praise thee, as I do this day: the father to the children shall make known
thy truth.
Isaiah 38:18-19
So Hezekiah believed the same thing the other inspired OT writers believed and taught. Isaiah was his prophet and teacher so he was no doubt instrumental in the things Hezekiah believed. What was it again?
When one dies they do not celebrate YHWH. They cannot hope for his truth. It is the living that praise him and pass along
THE TRUTH from Fathers to children. Hezekiah and Isaiah passed this doctrine to theirs no doubt.
How would they have reacted if one came along and told them
NOT SO brothers. What you are teaching is not true. YHWH has told
ME that you will find Sheol/Hades a very nice place full of activity and joy!
They would have believed he was attempting to overthrow the truth they were delivered by the Holy Spirit.
9:5 For the living know that they shall die: but
the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten.
Ecclesiastes 9:5
They would have quickly pointed them to the scriptures that would remind them that the dead are really dead.
Since there is no knowledge in Sheol/Hades where they were going they would not know any thing.
146:2
While I live will I praise the LORD: I will sing praises unto my God while I have
any being.
146:3 Put not your trust in princes, nor in the son of man, in whom there is no help.
146:4 His breath goeth forth, he returneth to his earth;
in that very day his thoughts perish. Psalms 146:4
Again we are taught the same truth. We praise YHWH while we have any
BEING. The living have being. They exist. When men die they exist no more. Their thoughts perish which means die. How could they even know who they were in
Sheol/Hades if their thoughts perished?
So in the light of the inspired revelations given to the Old Testament people what was their hope? Did they think they would never awaken from the sleep of death?
17:15 As for me, I will behold thy face in righteousness: I shall be satisfied,
when I awake, with thy likeness.
Psalms 17:15
They believed firmly in two things. First their death would be like sleeping. The writer says
WHEN I AWAKE.
Note carefully there he does not say
WHEN MY BODY AWAKES. No. It was
WHEN I AWAKE.
If he says he would awake he knew he would be sleeping. But if he knew he would one day wake up he knew he was going to be resurrected. The day would come he would live again!
So now we have a foundation of truth from scripture that we can compare with other teachings and judge for ourselves what is being added to it whether it agrees with the revelations YHWH gave to the Prophets or not.