Jami' al-Tirmidhi

Abu Hurairah narrated that : Allah's Messenger said: "Shall I tell you that for which Allah will wipe out your sins, and raise your ranks?" They said, "Of course Allah's Messenger!" He said: "Performing Wudu well in difficulty, and taking many steps to the Masajid, and waiting for Salat after Salat, That is the Ribat."