The Book Pertaining to Piety and Softening of Hearts (Kitab Al-Zuhd wa Al-Raqa'iq)
Muslim :: Book 42 : Hadith 7108
Abu Huraira reported that Allah's Messenger (may peace be upon him) said: One who looks after the orphan whether he is his relative or not, I and he would be together in Paradise like this, and Malik (explained it) with the gesture by drawing his index finger and middle finger close together.