SAHIH BUKHARI

Volume 1, Book 4, Number 176:

Narrated by Abu Huraira
Allah's Apostle said, "A person is considered in prayer as long as he is waiting for the prayer in the mosque as long as he does not do Hadath." A non-Arab man asked, "O Abii Huraira! What is Hadath?" I replied, "It is the passing of wind (from the anus) (that is one of the types of Hadath)."