The Republic by Plato Part 6 Page 48

How truly in earnest you are, Socrates! he said; I am sure of that; and yet most of your hearers, if I am not mistaken, are likely to be still more earnest in their opposition to you, and will never be convinced; Thrasymachus least of all.

Do not make a quarrel, I said, between Thrasymachus and me, who have recently become friends, although, indeed, we were never enemies; for I shall go on striving to the utmost until I either convert him and other men, or do something which may profit them against the day when they live again, and hold the like discourse in another state of existence.

You are speaking of a time which is not very near.

Rather, I replied, of a time which is as nothing in comparison with eternity.