Musnad Ahmad 1153:684

'Affan narrated to us, he said: Abu 'Awanah narrated to us, from Mutarrif, from 'Amir al-Sha'bi, from Masruq, from 'Aisha, that she said: "The Messenger of Allah (peace and blessings of Allah be upon him) would spend the night in a state of major ritual impurity (junub), then Bilal would come to him for the dawn prayer. He would stand up and perform ghusl, and I would look at the water trickling down his skin and his hair. Then I would hear his recitation for the dawn prayer, and he would remain fasting." Mutarrif said: I said to 'Amir: "In Ramadan?" He said: "It is the same to you."