Is a guarantee (Kafalah) valid if the term specified is unknown or indefinite?
Chapter on Guarantee (Daman)
Al-Mughni
Book of Assignment (Transfer of Debt)
Primary text
The guarantee (Kafalah) stipulated until an unknown term is invalid. This opinion is held by Al-Shafi'i. The reasoning is that there is no specified time when the guarantor can demand fulfillment. This ruling also applies to surety (Dhaman). If the term is set to an event like harvest ('Hasad') or reaping ('Jazaz') or giving ('Ata'a'), it is subject to the two established opinions regarding term setting in a sale. However, the sounder view here is that the guarantee is valid because it is a gratuitous donation that does not prevent the purpose of the guarantee from being achieved, similar to a vow (Nathr). This applies to any unknown term that does not impede the objective of the guarantee.
Supporting text
Regarding a case where a man guaranteed another person, stating, 'If you bring him at such and such a time, otherwise he owes what he owes,' Imam Ahmad expressed uncertainty, but he affirmed validity if the term was specified as 'such and such an hour.' This indicates that specifying an hour is binding, while uncertainty regarding a general time period (like harvest time) is questionable. If the term specified is a clear, limited time, such as 'the time of sunrise,' the guarantee is valid.