Musnad Ahmad 30:899

'Abd al-Rahman narrated to us, 'Abd al-Wahid ibn Ziyad narrated to us, 'Asim ibn Kulayb narrated to us, my father narrated to me, he said: I heard Abu Hurayrah saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The sermon (khutbah) which does not contain the testimony (shahadah) is like the amputated hand."