Musnad Abu Ya'la al-Mawsili 252:44

Harun ibn Ma'ruf narrated to us, Ibn Abi Hazim narrated to us, from his father, from Sahl ibn Sa'd, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "I and the guardian of the orphan are in Paradise," and he gestured with the index finger and the middle finger.