It is narrated from Sayyiduna Abu Fatimah al-Damri (may Allah be pleased with him) that he said: I said: O Messenger of Allah, tell us of a deed on which we may remain steadfast and do. He (peace and blessings be upon him) said: "Hold fast to emigration (hijrah), for there is nothing like it." I said: O Messenger of Allah, tell us of another deed on which we may remain steadfast and do. He (peace and blessings be upon him) said: "Hold fast to jihad, for there is no deed like it." I said: O Messenger of Allah, tell us of another deed on which we may remain steadfast and do. He (peace and blessings be upon him) said: "Hold fast to fasting, for there is no deed like it." I said: O Messenger of Allah, tell us of another deed on which we may remain steadfast and do. He (peace and blessings be upon him) said: "Hold fast to prostration, for you do not prostrate a single prostration to Allah except that Allah raises you a degree by it and removes a sin by it."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 19013