John Gill Commentary 2 Samuel 12:23

"But now he is dead, wherefore should I fast? can I bring him back again? I shall go to him, but he will not return to me." — 2 Samuel 12:23 (ASV)

But now he is dead, wherefore should I fast ?
&c.] And pray; it is to no purpose, no end can be thought to be answered by it:

can I bring him back again ?
from the state of the dead, bring him to life by fasting, and praying, and weeping; that is not to be expected:

I shall go to him ;
to the state of the dead, to the grave, where his body was, or would be; to heaven and eternal happiness, where his soul was, as he comfortably hoped and believed: from whence it appears, that the Old Testament saints did not suppose an annihilation at death; but believed the immortality of the soul, a future state after death of eternal life and bliss:

but he shall not return to me ;
in the present mortal state, though at the resurrection they should meet again.