Musannaf Ibn Abi Shayba 3:6091

Abu Mu'awiyah narrated to us, from Abd al-Rahman ibn Ziyad ibn An'am, from Abd al-Rahman ibn Rafi', from Abdullah ibn Amr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If the Imam sits and then breaks his wudu (hadath), his prayer is complete. And whoever is behind him, from those who caught the prayer with him, are upon the same [ruling]."