8 – Al-Qāsim related, from his father, from his grandfather: Al-Ashʿath ibn Qays purchased from Ibn Masʿūd a slave who belonged to the public treasury. When ʿAbd Allāh later demanded payment, the two disagreed about the price. Al-Ashʿath said, “I bought him from you for 10,000 dirhams,” while ʿAbd Allāh insisted, “I sold him to you for 20,000.” ʿAbd Allāh then said, “Choose someone to arbitrate between us.” Al-Ashʿath replied, “I appoint you to judge between me and yourself.” ʿAbd Allāh said, “Very well; I shall judge between us according to a ruling I heard from the Messenger of Allah (peace and blessings be upon him): ‘When the buyer and seller differ, the seller’s word prevails; the buyer must either accept it or the sale is rescinded.’

In another version, al-Qāsim narrates from his father, from his grandfather that the Messenger of Allah (peace and blessings be upon him) said: ‘If the two contracting parties dispute while the merchandise is still in its original state, the seller’s statement is accepted, or the transaction is annulled.’

A further narration from ʿAbd Allāh recounts that al-Ashʿath bought a slave from him; when payment was demanded they disagreed. ʿAbd Allāh said, “(The price was) 20,000,” and al-Ashʿath said, “10,000.” ʿAbd Allāh concluded, “I heard the Messenger of Allah (peace and blessings be upon him) say: ‘When the buyer and seller disagree, the seller’s word is to be taken, or they must cancel the sale.’”