From Sahih Bukhari (Hadith 5755):
Narrated Abu Huraira:The Prophet (ﷺ) said, "There is no Tiyara and the best omen is the Fal," Somebody said, "What is the Fal, O Allah's Messenger (ﷺ)?" He said, "A good word that one of you hears (and takes as a good omen)
Reference: Bukhari 5755