So act according to your wisdom, and do not let his gray hair go down to Sheol in peace.

"So act according to your wisdom, and do not let his gray hair go down to Sheol in peace. 1 Kings 2:6

What does progressive revelation mean?  Throughout history, the Lord did not reveal all of the truth at once.  There are over 900 years between the construction of the Temple and the birth of Christ.  After the Temple, Elijah, Elisha, Micah, Isaiah, Jeremiah, Ezekiel, Hosea, Amos, Obadiah, Joel, Jonah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah, and Malachi were born.  Those alive for the Temple construction would not have had access to most of what we consider to be messianic prophecies.  He would not even have had some of the Psalms.  Honestly what use would much of it have been to someone who existed before the Assyrian Empire, before even the Axial Age?  One of the things that was not imparted to the pre-axial Jewish people was a distinction between heaven and hell.  They believed in an underworld destination for both the righteous and the wicked.  This was a place where they would be silent and heard no more.  Below are some reference, most containing Sheol, that I hope will prove my point.  All but one are from the Iron Age and the one from Isaiah is from the Axial Age. 

For there is no mention of You in death; In Sheol who will give You thanks? Psalms 6:5

"What profit is there in my blood, if I go down to the pit? Will the dust praise You? Will it declare Your faithfulness?” Psalms 30:9

Let me not be put to shame, O LORD, for I call upon You; Let the wicked be put to shame, let them be silent in Sheol. Psalms 31:17

For my soul has *had enough troubles, And my life has drawn near to *Sheol. Psalms 88:3

Will You perform wonders for the dead? Will the departed spirits rise and praise You? Selah. Psalms 88:10

If I ascend to heaven, You are there; If I make my bed in Sheol, behold, You are there. Psalms 139:8

For the living know they will die; but the dead do not know anything, nor have they any longer a reward, for their memory is forgotten. Ecclesiastes 9:5

"For Sheol cannot thank You, Death cannot praise You; Those who go down to the pit cannot hope for Your faithfulness. Isaiah 38:18