one of the two attributes of the effective cause for Riba al-Fadl, so nisa' (delay in delivery) is permitted between them, like garments for animals.

Section: If one sells something from the items of Riba for something of a different type, and the effective cause ('illah) for Riba al-Fadl is the same in both, it is not permissible to separate before taking possession. If they do so, the contract is void. This is the opinion of al-Shafi'i. Abu Hanifah said: Taking possession is not a condition in these cases, unlike other properties of Riba, and like selling such items for one of the two forms of currency (gold or silver). Our evidence is the statement of the Prophet (peace and blessings of Allah be upon him): "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt; like for like, equal for equal, hand to hand." Narrated by Muslim (34). He (peace and blessings of Allah be upon him) also said: "If these classes differ, then sell as you wish, hand to hand" (35). Malik ibn Aws ibn al-Hadathan narrated that he requested a currency exchange for a hundred dinars. He said: "Talhah ibn Ubayd Allah called me, and we negotiated until he exchanged them with me. He took the gold and began turning it over in his hands, then said: 'Wait until my treasurer comes from al-Ghaba.' Umar was listening to this, and he said: 'No, by Allah, you shall not depart from him until you take [payment] from him.' The Messenger of Allah (peace and blessings of Allah be upon him) said: 'Gold for silver is Riba unless it is hand to hand, wheat for wheat is Riba unless it is hand to hand, dates for dates is Riba unless it is hand to hand, and barley for barley is Riba unless it is hand to hand.'" Muttafaqun alayhi (agreed upon) (39). The intended meaning...