Musnad Abu Ya'la al-Mawsili 129:8

Abu Khaythama narrated to us, Yazid bin Harun narrated to us, Humayd al-Tawil informed us, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) led us in the dawn prayer, and he heard the crying of a child in the row. We thought that he only did that out of mercy for him.