Section — Wouters, Manual of Moral Theology
§ IV. On Commodatum and Precarium
I. Notion of commodatum. Commodatum is a contract by which someone grants to another the use of a thing gratuitously, under this law, that the latter return the same thing at a determined time. It is said gratuitously; if something is demanded for the use of the thing, there is had a species of letting. Commodatum is called precarium if the use of the thing is granted revocably at the nod of the lender; the name of precarium comes from this, that the one receiving, in the case, is judged continually to pray that he may be able to retain the thing. Commodatum differs from mutuum, in which ownership of the thing is transferred (St. Alphonsus, III, 744, 745, 754).
II. Obligations of the lender. The lender is bound:
To manifest harmful defects to the borrower, if he knows them; otherwise he is bound for the damage that follows.
Not to demand the thing back before the time fixed.
To reimburse to the borrower extraordinary expenses necessary for preserving the thing (St. Alphonsus, III, 747).
III. Obligations of the borrower. He is bound:
To keep the thing diligently, and to bear ordinary expenses.
Not to use the thing except for the use signified by the contract or by the very nature of the thing; otherwise he is bound for the damage that follows.
To return the thing at the time fixed, or when the use has been completed.
To what extent he is held for the destruction of the thing and for other damages arising from juridical fault alone, see n. 1009.
Note. Sacred things should not be lent for a use repugnant to their nature (can. 1537).