The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1409
Abu Huraira reported: The Messenger of Allah (may peace be' upon him) said: He who purified himself in his house, and then he walked to one of the houses of Allah for the sake of performing a Fard (obligatory act) out of the Fara'id (obligatory acts) of Allah, both his steps (would be significant) as one of them would obliterate his sin and the second one would raise his status.