Musnad Ahmad 1153:1880

Muhammad ibn Ubayd narrated to us, he said: Wa’il ibn Dawud narrated to me, he said: I heard al-Bahiy narrating from Aisha, she said: "The Messenger of Allah, peace and blessings of Allah be upon him, never sent Zayd ibn Harithah in an army at all, but that he appointed him over them. And had he remained after him, he would have made him his successor."