Musnad Ahmad 1153:688

Hassan narrated to us, he said: Zuhair narrated to us, from Abu Ishaq, from al-Aswad, from Aisha, she said: "I have seen the Messenger of Allah, may Allah bless him and grant him peace, go out to prayer while his head was dripping. He was in a state of major ritual impurity (junub), so he performed ghusl, and he was intending to fast."