Sunan an-Nasa'i, Hadith 1449 ⓘ
It was narrated that 'Abdur-Rahman bin Yazid said: "Uthman prayer four (rak'ahs) in Mina until news of that reached 'Abdullah who said: 'I prayed two rak'ahs with the Messenger of Allah.'"
أَخْبَرَنَا عَلِيُّ بْنُ خَشْرَمٍ، قَالَ حَدَّثَنَا عِيسَى، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ يَزِيدَ، قَالَ صَلَّى عُثْمَانُ بِمِنًى أَرْبَعًا حَتَّى بَلَغَ ذَلِكَ عَبْدَ اللَّهِ فَقَالَ لَقَدْ صَلَّيْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم رَكْعَتَيْنِ .
also referenced under: Book 15, Hadith 17 (In-Book) & Volume 2, Book 15, Hadith 1450 (DarusSalam)