Abu Dharr reported: The Prophet, peace and blessings be upon him, said, “I was shown the good and evil deeds of my nation. I found that among their good deeds was removing harmful things from the road, and I found that among their evil deeds was their spit in the mosque that they left uncleaned.”
Source: Ṣaḥīḥ Muslim 553
Grade: Sahih (authentic) according to Muslim
عَنْ أَبِي ذَرٍّ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ عُرِضَتْ عَلَيَّ أَعْمَالُ أُمَّتِي حَسَنُهَا وَسَيِّئُهَا فَوَجَدْتُ فِي مَحَاسِنِ أَعْمَالِهَا الْأَذَى يُمَاطُ عَنْ الطَّرِيقِ وَوَجَدْتُ فِي مَسَاوِي أَعْمَالِهَا النُّخَاعَةَ تَكُونُ فِي الْمَسْجِدِ لَا تُدْفَنُ
553 صحيح مسلم كتاب المساجد ومواضع الصلاة باب النهي عن البصاق في المسجد في الصلاة وغيرها