As for the consent of the beneficiary of the guarantee and the guaranteed debtor, it is not a condition. However, if we know that it would harm the guaranteed debtor’s reputation, we may require it. This can be avoided by bringing the amount due and handing it over.

A guarantee is valid for an unknown liability if it will become known, as well as for borrowed items, usurped property, goods taken for price consideration, and liabilities arising from a sale. It is not valid for property held in trust; rather, it applies where there has been transgression with respect to it.

His statement, “A guarantee is valid for an unknown liability if it will become known”: guaranteeing an unknown liability that will become known is permissible. An example is what jurists call a market guarantee: a person undertakes to guarantee everything owed by the guaranteed debtor in his dealings in a particular market.

For example, in the gold market, a person may say: “I guarantee this man in every transaction conducted in the gold market.” This is permissible, even though it concerns an unknown liability.

It should be said, however, that there is no harm in guaranteeing an unknown liability, but we have mentioned that the amount of the debt should be specified, as should the person from whom he intends to borrow. For if he does not specify this, and gives a guarantee up to ten thousand, he may stand at one shop and say, “This guarantee is for ten thousand,” and purchase goods for ten thousand. He may then go to another shop, purchase goods for another ten thousand, and say, “This is the guarantee.” Unless he stipulates: whenever you present this document and purchase up to the amount I have guaranteed for you, let it be written beneath it, “The guaranteed amount has been exhausted.” In that case, there is no harm; otherwise, the borrower may manipulate the matter.

The evidence for the validity of guaranteeing an unknown liability that will become known is the saying of Allah, Most High: “Whoever brings it shall have a camel-load, and I guarantee it” [Yusuf 12:72]. A camel-load is not known precisely; it may be more or less, even though it is generally known. It may therefore be said that citing this verse as evidence is open to question, since the load may be known through customary practice and usage. But it may be said that there is a rationale for this, namely that