Is it permissible to take a pledge (rahn) or a guarantor (kafīl) from the seller in a forward sale (Salaf)?

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There are differing reports concerning taking a pledge or a guarantor in a Salaf transaction. The view prohibiting this is narrated by al-Marwazī, Ibn al-Qāsim, and Abū Ṭālib, and it is the preferred position of al-Kharqī and Abū Bakr. The justification for prohibition is that if the pledge or guarantor is taken for the principal capital of the Salaf, it is taken against something that is neither currently due nor destined to become due, as the capital has already been transferred to the buyer. If taken for the specified commodity (*al-muslam fīh*), the pledge is only valid for something that can be fully satisfied from the sale price of the pledged item, but the commodity of the Salaf cannot be satisfied from the pledge or the guarantor's liability. Furthermore, the creditor cannot be certain that the pledge will not perish while in their possession through wrongful action, meaning they would then be satisfying their right from something other than the item due in the Salaf, which contradicts the ruling that one who enters into a Salaf should not divert it to something else, as narrated by Abū Dāwūd. Additionally, accepting a guarantor implies substituting the liability of the guarantor for the liability of the original debtor, which is akin to taking a substitute consideration, which is impermissible.