Abu Muslim al-Khawlani says: He (Awf bin Malik, may Allah be pleased with him) is beloved to me and trustworthy in my view. Sayyiduna Awf bin Malik (may Allah be pleased with him) says: We were with the Messenger of Allah (peace and blessings be upon him), nine, eight or seven men, and he (peace and blessings be upon him) said: "Will you not pledge allegiance to the Messenger of Allah (peace and blessings be upon him)?" He (peace and blessings be upon him) repeated this three times, so we said: O Messenger of Allah, we have already pledged allegiance to you; so on what should we pledge allegiance to you? He (peace and blessings be upon him) said: "That you worship Allah and do not associate anything with Him, and that you offer the five prayers" - and he said one thing quietly - "that you do not ask people for anything."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15158