Musnad Ahmad 1159:2

Muhammad ibn Salamah narrated to us, from Ibn Ishaq, from Yazid ibn Abi Habib, from Suwayd ibn Qays, from Mu'awiyah ibn Hudayj, from Mu'awiyah, who said: I said to Umm Habibah, the wife of the Prophet, may Allah bless him and grant him peace: "Did the Messenger of Allah, may Allah bless him and grant him peace, pray in the garment in which he slept with you?" She said: "Yes, as long as he did not see any impurity on it."