Thawbān (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "Who can guarantee for me that he will never ask people for something, and I will guarantee Paradise for him?" So I said: "I do." Since then, Thawabān (may Allah be pleased with him) never asked anyone for anything.
The Hadīth means that whoever commits himself before the Prophet (may Allah's peace and blessings be upon him) not to ask people for their money or seek their help to fulfill his duties, whether much or little, he will guarantee for him Paradise. That is because refraining from asking people entails reliance on Allah, and is proof of one's strong hope and trust in Allah, the Almighty. So this person's reward is that Allah, the Exalted, admits him to Paradise. After Thawbān (may Allah be pleased with him) had heard this Hadīth, he committed himself before the Prophet (may Allah's peace and blessings be upon him) that he would not ask people for anything. It is reported from him, as in the narration of Ibn Mājah, "that his whip would fall down while he was riding, yet he would not ask anyone to hand it to him, rather he would get down and pick it himself. He did this in fulfillment of the promise that he committed himself to before the Messenger of Allah (may Allah's peace and blessings be upon him)."