Sunan Abi Dawud 1964
سنن أبي داود#1964Hasanحَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنِ الزُّهْرِيِّ، أَنَّ عُثْمَانَ بْنَ عَفَّانَ، أَتَمَّ الصَّلاَةَ بِمِنًى مِنْ أَجْلِ الأَعْرَابِ لأَنَّهُمْ كَثُرُوا عَامَئِذٍ فَصَلَّى بِالنَّاسِ أَرْبَعًا لِيُعْلِمَهُمْ أَنَّ الصَّلاَةَ أَرْبَعٌ .
Narrated Az-Zuhri: Uthman offered complete prayer at Mina for the sake of bedouins who attended (hajj) in large numbers that year. He led the people four rak'ahs in prayer in order to teach them that the prayer (i.e. noon or afternoon prayer) essentially contained four rak'ahs
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:
In-book reference: 11:244