Sahih al-Bukhari 415
صحيح البخاري#415Sahihحَدَّثَنَا آدَمُ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنَا قَتَادَةُ، قَالَ سَمِعْتُ أَنَسَ بْنَ مَالِكٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " الْبُزَاقُ فِي الْمَسْجِدِ خَطِيئَةٌ، وَكَفَّارَتُهَا دَفْنُهَا ".
Narrated Anas bin Malik:The Prophet (ﷺ) said, "Spitting in the mosque is a sin and its expiation is to bury it
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 8:65