Sahih Bukhari
Sahih Bukhari Volume 001, Book 008, Hadith Number 405.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 08. Prayers (Salat)
Narated By Anas bin Malik : The Prophet said, "A faithful believer while in prayer is speaking in private to his Lord, so he should neither spit in front of him nor to his right side but he could spit either on his left or under his foot."