Abu Ayyaz says that once Marwan sent a messenger to Umm Salama to ask her about a certain issue. She sent her freed slave to Marwan. She said that if it was obligatory for the Prophet (peace be upon him) to perform ghusl by choice, even then the Prophet (peace be upon him) would fast and would not miss it. The slave returned and conveyed this. Then Marwan sent his messenger to Aisha, and she also sent her slave to Marwan, and she gave the same answer. So Marwan said to the messenger, "Go to Abu Huraira (may Allah be pleased with him) and tell him this." So he went to Abu Huraira (may Allah be pleased with him) and told him this hadith from Umm Salama and Aisha. He said, "They both know better."