Sahih Al Bukhari – Book of Characteristics Of Prayer

Volumn 001, Book 012, Hadith Number 726.
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Narated By ‘Abdullah bin Abi Qatada : My father said, “The Prophet in Zuhr prayers used to recite Al-Fatiha along with two other Suras in the first two Rakat: a long one in the first Rak’a and a shorter (Sura) in the second, and at times the verses were audible. In the ‘Asr prayer the Prophet used to recite Al-Fatiha and two more Suras in the first two Rakat and used to prolong the first Rak’a. And he used to prolong the first Rak’a of the Fajr prayer and shorten the second.