Musnad Abu Ya'la al-Mawsili 147:11

Abu al-Rabi' al-Zahrani narrated to us, Hammad narrated to us, Ayyub narrated to us, from Anas ibn Malik, who said: I have never seen anyone more merciful to children than the Messenger of Allah, may Allah bless him and grant him peace. He had a wet nurse for his son Ibrahim in the furthest part of Medina, and her husband was a blacksmith. He would go to him, and the boy would come to him with traces of smoke upon him, so he would embrace him, kiss him, and smell him.