Hi Ian,
All die and we have the word of Scripture for that.
Eze 18:20 The soul who sins shall die.
Rom 3:23 for all have sinned and fall short of the glory of God,
Yes all, even the righteous, die and go to the grave. We have Scripture that show David died.
1Ki 2:10 So David rested with his fathers, and was buried in the City of David.
Now in the Psalms David frequently cries out to God to save him from being killed by his enemies or do not let him "go down to the pit."
Psa 30:8 I cried out to You, O LORD;
And to the LORD I made supplication:
v. 9 "What profit is there in my blood,
When I go down to the pit?
Will the dust praise You?
Will it declare Your truth?
v. 10 Hear, O LORD, and have mercy on me;
LORD, be my helper!"
In Psalms 30 we see how David speaks of how God spared his life.
Psa 30:3 O LORD, thou hast brought up my soul from the grave: thou hast kept me alive, that I should not go down to the pit. (KJ)
Psa 30:3 you kept me from the grave. I was on my way to the depths below, but you restored my life. (GNB)
In Isaiah 38 it speaks of our life being over and not being able to do anything in the grave.
Isa 38:18 For Sheol (the grave) cannot thank You, death cannot praise You; those who go down to the pit cannot hope for Your faithfulness. (RSV)
So look at Scripture from the perspective that all do die and that the grave or pit in a hole in the ground where dead people are cast/buried. Hope that helps.
mercy, peace and love
Kat