Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that a man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah (peace and blessings be upon him)! Teach me a deed that is equal to jihad. He (peace and blessings be upon him) said: "I do not find such a deed." Then he (peace and blessings be upon him) said: "Are you able, when the fighter goes out (for jihad), to enter the mosque and stand (in prayer) without slackening, and fast without breaking your fast?" He said: I am not able to do that. Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: The horse of the fighter prances about on its tether, and good deeds are written for him (because of it).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18488