And in the laying of bricks and stones is the just man a more useful
or better partner than the builder?

Quite the reverse.

Then in what sort of partnership is the just man a better partner
than the harp-player, as in playing the harp the harp-player
is certainly a better partner than the just man?

In a money partnership.

Yes, Polemarchus, but surely not in the use of money; for you do not
want a just man to be your counsellor the purchase or sale of a horse;
a man who is knowing about horses would be better for that,
would he not?

Certainly.

And when you want to buy a ship, the shipwright or the pilot would
be better?

True.

Then what is that joint use of silver or gold in which the just man
is to be preferred?

When you want a deposit to be kept safely.

You mean when money is not wanted, but allowed to lie?