Musnad Ahmad 307:20

'Attab ibn Ziyad narrated to us, 'Abdullah—meaning Ibn al-Mubarak—narrated to us, Musa ibn 'Uqbah narrated to us, from 'Abd al-Rahman ibn Zayd ibn 'Uqbah, from Anas ibn Malik, who said: I, Ubayy ibn Ka'b, and Abu Talhah were sitting, and we ate meat and bread. Then I called for water for ablution. They both said: "Why are you performing ablution?" I said: "Because of this food that we have eaten." They both said: "Do you perform ablution because of the good things? He who was better than you did not perform ablution."