Volume 7 · Book 71 · Hadith 651
Narrated Abu Huraira: The Prophet said, "There is no Tiyara and the best omen is the Fal," Somebody said, "What is the Fal, O Allah's Apostle?" He said, "A good word that one of you hears (and takes as a good omen)."
— Sahih Bukhari, Volume 7, Book 71: Medicine, Hadith #651