The simplest scripture defining what death is will be found in James 2:26, "The body without the spirit is dead."
Death means the separation of life from the body.
Death is never the end of existence. This Luke 16:19-31 would plainly teach.
The answer of the Lord to the Sadducees in Luke 20, when speaking of the patriarchs who had died many years before, was, "All live unto Him"-(see verse 38).
The blessedness of those of faith in the interval between death and resurrection is not revealed in the Old Testament. It has now come to light through Paul's gospel (2 Tim. 1:9,10).
Eccl. 3:19 is simply all that man could know by viewing things "under the sun." God is showing in that book the utter inability of man to find out the things that belong to revelation.
The second death is the separation of the whole man from God forever. What a solemn voice of warning!
The fact of a "second death" proves that the first one was not cessation of being.
"We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord." 2 Cor. 5:8.
DEATH and judgment are behind us,
Grace and glory are before;
All the billows rolled o'er Jesus,
There they spent their utmost power.
"First-fruits" of the resurrection,
He is risen from the tomb:
Now we stand in new creation,
Free, because beyond our doom.
Jesus died, and we died with Him,
"Buried" in His grave we lay,
One with Him in resurrection,
Now "in Him" in heaven's bright day.