Sahih Bukhari
Sahih Bukhari Volume 001, Book 008, Hadith Number 404.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 08. Prayers (Salat)
Narated By Anas : The Prophet said, "None of you should spit in front or on his right but he could spit either on his left or under his foot."