It was narrated from Abu Hurairah that:
The Prophet said: "Sins are expiated by well-performed ablution despite difficulties, increasing the number of steps one takes towards the mosque, (and waiting for the next prayer after prayer)." (IT)
English reference (IT): Vol. 1, Book 1, Hadith 428 (IT)
Arabic reference (IT): Book 1, Hadith 463 (IT)