Sayyidina Abu Huraira (RA) narrated that Allah's Messenger (SAW) said, "Shall I not tell
you of something by which Allah erases sins and elevates ranks?" They (the sahabah)
said, 'Of course, 0 Messenger of Allah!" He said, "To perfect ablution even in trying
conditions, to go towards mosques very often and to wait for the next salah after
offering one. This is ribat (guarding the frontiers)."
[Bukhari 7733,Muslim 251, Nisai 90]