Sahih Al Bukhari Hadith Number 778

Narrated `Abdullah bin Abi Qatada: My father said, “The Prophet (peace be upon him) used to recite Al-Fatiha along with another Sura in the first two rak`at of the Zuhr and `Asr prayers. A verse or so was audible at times and he used to prolong the first rak`a.”

10  Call to Prayers (Adhaan)
Hadith number 778
Volume no 1
Chapter: 109 ((In a quiet prayer) if the Imam recites a Verse or so audibly)