Sunan Abi Dawud 1961
سنن أبي داود#1961Da'ifحَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، أَخْبَرَنَا ابْنُ الْمُبَارَكِ، عَنْ مَعْمَرٍ، عَنِ الزُّهْرِيِّ، أَنَّ عُثْمَانَ، إِنَّمَا صَلَّى بِمِنًى أَرْبَعًا لأَنَّهُ أَجْمَعَ عَلَى الإِقَامَةِ بَعْدَ الْحَجِّ .
Narrated Az-Zuhri: Uthman prayed four rak'ahs at Mina because he resolved to stay there after hajj
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-AlbaniDaif
Muhammad Muhyi Al-Din Abdul HamidDaif
Zubair Ali ZaiDaif
In-book reference: 11:241