him a loan at
some future time.

Reply Obj. 5: He who lends money transfers the ownership of the money
to the borrower. Hence the borrower holds the money at his own risk
and is bound to pay it all back: wherefore the lender must not exact
more. On the other hand he that entrusts his money to a merchant or
craftsman so as to form a kind of society, does not transfer the
ownership of his money to them, for it remains his, so that at his
risk the merchant speculates with it, or the craftsman uses it for
his craft, and consequently he may lawfully demand as something
belonging to him, part of the profits derived from his money.

Reply Obj. 6: If a man in return for money lent to him pledges
something that can be valued at a price, the lender must allow for
the use of that thing towards the repayment of the loan. Else if he
wishes the gratuitous use of that thing in addition to repayment, it
is the same as if he took money for lending, and that is usury,
unless perhaps it were such a thing as friends are wont to lend to
one another gratis, as in the case of the loan of a book.

Reply Obj. 7: If a man wish to sell his goods at a higher price than
that which is just, so that he may wait for the buyer to pay, it is
manifestly a case of usury: because this waiting for the payment of
the price has the character of a loan, so that whatever he demands
beyond the just price in consideration of this delay, is like a price
for a loan, which pertains to usury. In like manner if a buyer wishes
to buy goods at a lower price than what is just, for the reason that
he pays for the goods before they can be delivered, it is a sin of
usury; because again this anticipated payment of money has the
character of a loan, the price of which is the rebate on the just
price of the goods sold. On the other hand if a man wishes to allow a
rebate on the just price in order that he may have his money sooner,
he is not guilty of the sin of usury.
_______________________

THIRD ARTICLE [II-II, Q. 78, Art. 3]

Whether a Man Is Bound to Restore Whatever Profits He Has Made Out of
Money Gotten by Usury?

Objection 1: It would seem that a man is bound to restore whatever
profits he has made out of money gotten by usury. For the Apostle
says (Rom. 11:16): "If the root be holy, so are the branches."
Therefore likewise if the root be rotten so are the branches. But the
root was infected with usury. Therefore whatever profit is made
therefrom is infected