Narrated Abu Huraira (may Allah be pleased with him):
A man came to the Messenger of Allah (peace and blessings of Allah be upon him) and said, "Tell me of an act of worship that is equal in reward to Jihad." The Prophet (peace and blessings of Allah be upon him) replied, "I do not find any such act." (Then) the Prophet (peace and blessings of Allah be upon him) said, "Can you do this: when a Mujahid goes out (for Jihad), you stand in your mosque (praying) without showing any laziness, and you keep fasting continuously without breaking it?" He said, "Who can do that?"