Musnad Ahmad 1119:24

Qutaybah ibn Sa'id narrated to us, he said: Ibn Lahi'ah narrated to us, from Yazid ibn Abi Habib, from Rabi'ah ibn Laqit, from 'Awf ibn Malik al-Ashja'i, who said: I entered upon the Prophet, may Allah bless him and grant him peace, among six, seven, or eight people. He said to us: "Pledge allegiance to me." We said: "O Prophet of Allah, we have already pledged allegiance to you." He said: "Pledge allegiance to me." So we pledged allegiance to him, and he took from us what he took from the people. Then he followed that with a quiet word, saying: "Do not ask people for anything."