Musannaf Ibn Abi Shayba 3:5140

Hatim ibn Isma'il narrated to us, from Humayd ibn Sakhr, from al-Maqburi, from Abu Hurayrah, who said: I heard the Messenger of Allah (may Allah bless him and grant him peace) say: "Whoever comes to my mosque, and he did not come except for a good that he teaches or learns, then he is in the position of the mujahid in the way of Allah. And whoever comes to it for other than that, then he is in the position of a man looking at the property of someone else."