Sahih Bukhari Volume 001, Book 004, Hadith Number 137.

Narated By Abu Huraira : Allah's Apostle said, "The prayer of a person who does ,Hadath (passes, urine, stool or wind) is not accepted till he performs (repeats) the ablution." A person from Hadaramout asked Abu Huraira, "What is 'Hadath'?" Abu Huraira replied, " 'Hadath' means the passing of wind from the anus."