Sahih Bukhari Volume 004, Book 054, Hadith Number 536.
Narated By Abu Huraira : Allah's Apostle said, "Once while a prophet amongst the prophets was taking a rest underneath a tree, an ant bit him. He, therefore, ordered that his luggage be taken away from underneath that tree and then ordered that the dwelling place of the ants should be set on fire. Allah sent him a revelation: "Wouldn't it have been sufficient to burn a single ant? (that bit you): (See Page 162, chapter No. 153).