Sahih Bukhari Volume 008, Book 073, Hadith Number 027.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 73. Good Manners and Form (Al-Adab)
Narated By 'Aisha : A Bedouin came to the Prophet and said, "You (people) kiss the boys! We don't kiss them." The Prophet said, "I cannot put mercy in your heart after Allah has taken it away from it."