Sahih Bukhari Volume 1, Book 12, Hadith Number 725

Narated By Jabir bin Samura : Sa’d said, “I used to pray with them a prayer similar to that of Allah’s Apostle (the prayer of Zuhr and ‘Asr) reducing nothing from them. I used to prolong the first two Rakat and shorten the last two Rak’at.” ‘Umar said to Sa’d “This was what we thought about you.”