Abdul 'Aziz bin Abi Hazim عبد العزيز بن أبي حازم · The Chapters on Business Transactions

"The contractual obligation regarding a slave lasts for three days." (1)

"I heard 'Umar bin Al-Khattab say: 'The Messenger of Allah (ﷺ) said: "Exchanging gold for gold is usury unless it is done on the spot. (Exchanging) wheat for wheat is usury, unless it is done on the spot. (Exchanging) barley for barley is usury unless it is done on the spot. (Exchanging) dates for dates is usury, unless it is done on the spot."