In 1 Corinthians 15 Paul talked about eternity.

"Behold, I shew you a mystery; We shall not
all sleep, but we shall all be changed,
In a moment, in the twinkling of an eye, at
the last trump: for the trumpet shall sound,
and the dead shall be raised incorruptible,
and we shall be changed.
For this corruptible must put on incorruption,
and this mortal must put on immortality.
So when this corruptible shall have put on
incorruption, and this mortal shall have put
on immortality, then shall be brought to pass
the saying that is written, Death is swallowed
up in victory." (verses 51-54)