Sahih Muslim
Sahih Muslim 552 b
The prohibition of spitting in the masjid, during prayer and at other times. The prohibition of a praying person spitting in front of him or to his right
Arabic hadith text
حَدَّثَنَا يَحْيَى بْنُ حَبِيبٍ الْحَارِثِيُّ، حَدَّثَنَا خَالِدٌ، - يَعْنِي ابْنَ الْحَارِثِ - حَدَّثَنَا شُعْبَةُ، قَالَ سَأَلْتُ قَتَادَةَ عَنِ التَّفْلِ، فِي الْمَسْجِدِ فَقَالَ سَمِعْتُ أَنَسَ بْنَ مَالِكٍ، يَقُولُ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ "التَّفْلُ فِي الْمَسْجِدِ خَطِيئَةٌ وَكَفَّارَتُهَا دَفْنُهَا "
Translation
Shu'ba reported
I asked Qatada about spitting, in the mosque. He said: I heard Anas b. Malik say: I heard the Messenger of Allah (ﷺ) say: Spitting in the mosque is a sin, and its expiation is that it should be buried.