Sahih Bukhari, Chapter: Prayer at Night (Tahajjud)

I heard Abu Ash-sha'tha' Jabir saying, "I heard Ibn Abbas saying, 'I offered with Allah's Apostle eight Rakat (of Zuhr and 'Asr prayers) together and seven Rakat (the Maghrib and the 'Isha' prayers) together.' " I said, "O Abu Ash-shatha! I think he must have prayed the Zuhr late and the 'Asr early; the 'Isha early and the Maghrib late." Abu Ash-sha'tha' said, "I also think so." (See Hadith No. 518 Vol. 1).