It is narrated from Hazrat Umm Salamah (may Allah be pleased with her) that once the Prophet (peace and blessings be upon him) was in my house when a man came and said, "O Messenger of Allah, how much zakat is obligatory on such an amount of wealth?" The Prophet (peace and blessings be upon him) told him the amount. He said, "Such and such a person has wronged me." It was found that the excess was equal to one sa’ (a measure). The Prophet (peace and blessings be upon him) said, "What will become of you when you are wronged by more than this?"