Musnad Ahmad 1:64

Musa ibn Dawud narrated to us, Abdullah ibn al-Mu'ammal narrated to us, from Ibn Abi Mulaykah, who said: It would sometimes happen that the nose-rein would fall from the hand of Abu Bakr al-Siddiq, may Allah be pleased with him. He said: So he would strike the arm of his she-camel, and she would kneel, and he would take it. He said: So they said to him, "Will you not command us so that we may hand it to you?" He said: "Indeed, my beloved, the Messenger of Allah, may Allah bless him and grant him peace, commanded me not to ask people for anything."