Musnad Ahmad 830:54

Abu Kamil narrated to us, Hammad narrated to us, from Ziyad al-A'lam, from al-Hasan, from Abu Bakrah: "The Prophet, peace and blessings of Allah be upon him, entered into the dawn prayer, then he gestured to them: 'Stay in your places.' He went away, then he came back while his head was dripping [with water], and he led them in prayer."