Mishkat al-Masabih 282, 283

Abu Huraira reported God’s messenger as saying, “Shall I not guide you to something for which God blots out sins and raises men's ranks?” When his hearers expressed their desire that he should tell them, he said, “Performing complete ablution although circumstances make it difficult, travelling far to mosques, and looking expectantly to the next time of prayer after prayers have been said. That is the defence of the frontier.”* The tradition of Malik b. Anas has, “That is the defence of the frontier; that is the defence of the frontier. He repeated it twice.” *Here meant in a spiritual sense, as a defence against infidelity and wrongdoing. Muslim transmitted it. Tirmidhi’s version has thrice.