Musnad Ahmad 830:86

'Affan narrated to us, Hammad ibn Salamah narrated to us, Ziyad al-A'lam narrated to us, from al-Hasan, from Abu Bakrah, that the Messenger of Allah (peace and blessings of Allah be upon him) entered into the dawn prayer, then he gestured to his companions, meaning: "Stay in your places." He went away and came back while his head was dripping [with water], and he led the people in prayer.