أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ الْبُصَاقُ فِي الْمَسْجِدِ خَطِيئَةٌ وَكَفَّارَتُهَا دَفْنُهَا ‏"‏ ‏.‏

It was narrated that Anas said

"The Messenger of Allah (ﷺ) said: 'Spitting in the Masjid is a sin, and its expiation is to bury it.'"