Musnad Ahmad 1153:1442

'Abd al-Rahman narrated to us, he said: Za'idah narrated to us, from al-Suddi, from 'Abd Allah al-Bahiy, from 'A'ishah, that the Prophet, peace and blessings of Allah be upon him, said to the slave girl while he was in the mosque: "Hand me the prayer mat." She said: He wanted to spread it out to pray upon it. She said: "I am menstruating." He said: "Indeed, her menstruation is not in her hand."