Musnad Ahmad 30:1398

'Affan narrated to us, 'Abd al-Wahid ibn Ziyad narrated to us, he said: 'Asim ibn Kulayb informed us, my father narrated to me, he said: I heard Abu Hurayrah say: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Every sermon (khutbah) that does not contain the testimony (shahadah) is like a hand afflicted with leprosy (al-jadhma')."