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.