It was narrated from Qasim bin 'Abdur Rahman from his father that :
Abdullah bin Mas'ud sold one of the slaves from the state[1] to Ash'ath bin Qais, and they differed concerning the price. Ibn Mas'ud said: I sold him to you for twenty thousand,' but Ash'ath bin Qais said: I bought him from you for ten thousand. 'Abdullah said: If you want, I will tell you a Hadith which I heard from the Messenger of Allah (ﷺ) He said: Tell me it. He said: I heard the Messenger of Allah (ﷺ) say: 'If two parties to a transaction differ, and they have no proof, and the sale item remains (unredeemed), then what the seller says is valid. Or they may cancel the transaction. He said: I want to cancel the transaction. And he cancelled it.