Sunan Abi Dawud 482
سنن أبي داود#482Sahihحَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا حَمَّادٌ، أَخْبَرَنَا سَعِيدٌ الْجُرَيْرِيُّ، عَنْ أَبِي الْعَلاَءِ، عَنْ مُطَرِّفٍ، عَنْ أَبِيهِ، قَالَ أَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم وَهُوَ يُصَلِّي فَبَزَقَ تَحْتَ قَدَمِهِ الْيُسْرَى .
Abu al-‘Ala’ reported on the authority of his father:I came to the Messenger of Allah(ﷺ) who was saying prayer. He spat beneath his left foot
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 Muslim (554)
In-book reference: 2:92