An example of istishab which is also regarded as proof for its validity comes from the Prophet’s teaching of what to do when a person with ablution is in doubt of having spoilt his ablution by passing wind. The Prophet (صلى الله عليه وسلم) taught that such person’s ablution was intact unless the flatulence was certain from the perception of its sound or smell.
Sahih al-Bukhari, no.137; Sahih Muslim, no.98-99
