Musnad Ahmad 1156:122

Rawh and ‘Abd al-Wahhab narrated to us, they said: Sa‘id narrated to us, from Qatadah, from Sa‘id ibn al-Musayyib, from ‘Amir ibn Abi Umayyah, the brother of Umm Salamah, from Umm Salamah, that she said: "The Messenger of Allah (may Allah bless him and grant him peace) would wake up in a state of major ritual impurity (janabah), then he would wake up fasting."