It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that he said: "I prayed behind the Messenger of Allah (peace and blessings be upon him) eight rak'ahs together and seven rak'ahs together." (That is, he combined the Zuhr and Asr prayers, and the Maghrib and Isha prayers.)
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12750