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 at another’s property.” Ibn Majah and Baihaqi, in Shu'ab al-iman, transmitted it.
Source: sunnah.com
Other translations
Arabic
عَنْ أَبِي هُرَيْرَةَ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «مَنْ جَاءَ مَسْجِدي هَذَا لم يَأْته إِلَّا لِخَيْرٍ يَتَعَلَّمُهُ أَوْ يُعَلِّمُهُ فَهُوَ بِمَنْزِلَةِ الْمُجَاهِدِ فِي سَبِيلِ اللَّهِ وَمَنْ جَاءَ لِغَيْرِ ذَلِكَ فَهُوَ بِمَنْزِلَةِ الرَّجُلِ يَنْظُرُ إِلَى مَتَاعِ غَيْرِهِ» . رَوَاهُ ابْنُ مَاجَهْ وَالْبَيْهَقِيُّ فِي شُعَبِ الْإِيمَانِ
sunnah.com