عَنِ الْقَاسِمِ قَالَ اخْتَلَفَ عَبْدُ اللَّهِ وَالْأَشْعَثُ فَقَالَ ذَا بِعَشْرَةٍ وَقَالَ ذَا بِعِشْرِينَ قَالَ اجْعَلْ بَيْنِي وَبَيْنَكَ رَجُلًا قَالَ أَنْتَ بَيْنِي وَبَيْنَ نَفْسِكَ فَقَالَ أَقْضِي بِمَا قَضَى بِهِ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِذَا اخْتَلَفَ الْبَيِّعَانِ وَلَمْ يَكُنْ بَيِّنَةٌ فَالْقَوْلُ قَوْلُ الْبَائِعِ أَوْ يَتَرَادَّانِ الْبَيْعَ
Qasim says: There was a disagreement between Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) and Sayyiduna Ash'ath bin Qais (may Allah be pleased with him). The former said: It is of ten, but the latter said: It is of twenty. Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: Appoint someone between me and yourself (so that he may decide). Sayyiduna Ash'ath (may Allah be pleased with him) said: I appoint you yourself. Hearing this, Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: Then I will decide as the Messenger of Allah (peace and blessings be upon him) decided. The Messenger of Allah (peace and blessings be upon him) said: When there is a disagreement between two people involved in a transaction, and neither has any evidence, then the statement of the seller will be relied upon, or both may annul the sale.