The World Federation One Stop Fiqh

Ruling 2343

The surety must be of the age of legal responsibility (bāligh), sane (ʿāqil), and no one must have compelled him [to enter into the kafālah agreement]. In addition, he must be able to make the person for whom he is the surety appear, and he must not be foolish with finances (safīh).1 Furthermore, he must not have been proclaimed bankrupt (mufallas) in the event that making the debtor appear requires him to have disposal over his property.

1 Ruling 2091 provides further clarification of this term: it refers to someone who spends his wealth in futile ways.