Sahih Al Bukhari – Book of Characteristics Of Prayer

Volumn 001, Book 012, Hadith Number 743.
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Narated By 'Abdullah bin Abi Qatada RA : My father said, "The Prophet  PBUH used to recite Al-Fatiha followed by another Sura in the first two Rakat of the prayer and used to recite only Al-Fatiha in the last two Rakat of the Zuhr prayer. Sometimes a verse or so was audible and he used to prolong the first Rak'a more than the second and used to do the same in the 'Asr and Fajr prayers."