It was narrated that Abu Hurairah said:
"The Messenger of Allah said: 'When anyone of you cleans himself, he should not clean himself with his right hand. Let him clean himself with his left hand.'" (TH)
English reference (TH): Vol. 1, Book 1, Hadith 312 (TH)
Arabic reference (TH): Book 1, Hadith 333 (TH)