(76) باب الصَّلاَةِ بِمِنًى
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.
Reference: Sunan Abi Dawud 1964
In-book reference: Book 11, Hadith 244
English translation: Book 10, Hadith 1959