Abu Huraira said that he heard God’s Messenger say, “If anyone comes to this mosque of mine, coming only for some good which he will learn or teach, he ranks a mujahid in God’s path; but if anyone comes for some other purpose, he ranks as a man who looks [enviously] at another’s property.”
Ibn Majah and Baihaqi, in Shu'ab al-iman, transmitted it.