Sahih Al Bukhari Hadith Number 715

Narrated Abu Huraira: The Prophet (peace be upon him) prayed two rak`at of Zuhr prayer (instead of four) and he was told that he had prayed two rak`at only. Then he prayed two more rak`at and finished them with the Taslim followed by two prostrations.

10  Call to Prayers (Adhaan)
Hadith number 715
Volume no 1
Chapter: 69 ( Can the Imam depend on the people’s saying if he is in doubt (about a certain matter)?