Another ruling concerning guarantee is that the guarantor’s knowledge of the principal debtor is not a condition for validity. He may say, for example, “Whoever borrows from you, I stand surety for him.” Likewise, the guarantor does not have to know the creditor; in fact, neither the creditor’s nor the debtor’s consent is required, and therefore their precise identities need not be specified.

A further point is that a guarantee may apply to a determinate sum as well as to an indeterminate one, provided the latter can ultimately be ascertained. The Qur’an says, “And whoever brings it shall have a camel-load, and I hereby pledge myself for it” (Yūsuf 12:72). The amount represented by “a camel-load” is initially unknown, yet it can be measured, and the verse thus proves the permissibility of such a guarantee.

It is also valid to guarantee the ʿuhda (liability) of a sale—that is, to undertake reimbursement of the price should the purchased item turn out to belong to someone other than the seller.

In addition, one may guarantee whatever obligations may fall upon a person, such as any debts or comparable liabilities that might subsequently become binding on him.