It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him): One day the Prophet (peace and blessings be upon him) was sitting among a group of his Companions. He (peace and blessings be upon him) raised his hand and said: "Who will pledge allegiance to me?" He said it three times, but no one stood up except Sayyiduna Thawban (may Allah be pleased with him). He said: May my father and mother be sacrificed for you! We pledged allegiance to you once, and now I pledge allegiance to you a second time. So, O Messenger of Allah, on what shall I pledge allegiance to you? He said: "On the condition that you will not ask people for anything, and for you is Paradise." He said: O Messenger of Allah! If I pledge allegiance to you and do not ask people for anything, will I have Paradise? He said: "Yes, if Allah wills." He said: No, by the One who sent you with the truth! As long as I remain in this world, I will not ask anyone for anything.
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7861