Musnad Ahmad 482:19

'Attab ibn Ziyad narrated to us, he said: Abdullah narrated to us, he said: Ibn Lahi'ah narrated to us, Yazid ibn 'Amr al-Mu'afiri informed me, from someone who heard 'Uqbah ibn 'Amir saying: "The Messenger of Allah, peace and blessings of Allah be upon him, sent me as a collector [of Zakat]. I asked his permission for us to eat from the charity, and he gave us permission."