Musnad Abu Ya'la al-Mawsili 117:92

Abu al-Rabi' narrated to us, al-Harith bin 'Ubayd narrated to us, from Thabit, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) sent me on an errand. I passed by some boys and sat with them, so I was delayed in returning to him. He came out and saw me with the boys, so he greeted them.