The Rites of Hajj (Kitab Al-Manasik Wa'l-Hajj)
11/76. Chapter:
The Salat At Mina
Sunan Abi Dawud
حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، أَخْبَرَنَا ابْنُ الْمُبَارَكِ، عَنْ يُونُسَ، عَنِ الزُّهْرِيِّ، قَالَ لَمَّا اتَّخَذَ عُثْمَانُ الأَمْوَالَ بِالطَّائِفِ وَأَرَادَ أَنْ يُقِيمَ بِهَا صَلَّى أَرْبَعًا قَالَ ثُمَّ أَخَذَ بِهِ الأَئِمَّةُ بَعْدَهُ .
Narrated Az-Zuhri: When Uthman placed his property at at-Ta'if and intended to settle there, he prayed four rak'ahs. The rulers after him followed the same practice.
Reference : Sunan Abi Dawud 1963In-book reference : Book 11, Hadith 243English translation : Book 10, Hadith 1958