Sunan Abi Dawud 476
سنن أبي داود#476Sahihحَدَّثَنَا أَبُو كَامِلٍ، حَدَّثَنَا يَزِيدُ، - يَعْنِي ابْنَ زُرَيْعٍ - عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " النُّخَاعَةُ فِي الْمَسْجِدِ " . فَذَكَرَ مِثْلَهُ .
Anas b. Malik reported:The Messenger of Allah(ﷺ) said: Spitting phlegm in the mosque... The narrator then transmitted the rest of the tradition to the same effect
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:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih
In-book reference: 2:86