It is narrated from Hazrat Abu Umamah (may Allah be pleased with him) that once I presented myself before the Noble Prophet (peace and blessings be upon him) and requested, "Command me to do an action that will admit me into Paradise." The Noble Prophet (peace and blessings be upon him) said, "Make fasting obligatory upon yourself, for there is no deed like fasting." Then I again presented myself in the court of the Messenger (peace and blessings be upon him), and the Noble Prophet (peace and blessings be upon him) said, "Continue to make fasting obligatory upon yourself."
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 22149