Sayyiduna Abu Umamah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) sent out a detachment, and (the narrator) went on to mention the hadith. I said: O Messenger of Allah (peace and blessings be upon him)! Give me a command that will benefit me. He (peace and blessings be upon him) said: "Hold fast to (fasting), for there is no deed like it." After that, Abu Umamah (may Allah be pleased with him) would not be met except in a state of fasting, he, his servant and his wife as well (were in that state). When smoke was seen in their house during the day, we would think that a guest had come. Then I came to the Messenger of Allah (peace and blessings be upon him) and said: O Messenger of Allah (peace and blessings be upon him)! You told me something, and I hope Allah will bless it. Tell me something else. He (peace and blessings be upon him) said: "Know that you do not perform any prostration except that through it Allah raises your rank, a good deed is written for you, and your sin is wiped away."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8480