Musnad Ahmad 1153:282

Ibn Numayr narrated to us, Hisham narrated to us, from his father, from Aisha, who said: A Bedouin came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, do you kiss children? By Allah, we do not kiss them." The Messenger of Allah, may Allah bless him and grant him peace, said: "I have no power [to help you] if Allah, the Almighty and Majestic, has removed mercy from your heart."