Musannaf Ibn Abi Shayba 35:59

Ibn ‘Uyaynah narrated to us, from ‘Amr, from Jabir ibn Zayd, from Ibn ‘Abbas, who said: I prayed with the Prophet (peace and blessings of Allah be upon him) eight [rak‘ahs] together and seven [rak‘ahs] together. He [the narrator] said: I said, "O Abu al-Sha‘tha’, I think it was the end of Dhuhr and the beginning of ‘Asr, and the end of Maghrib and the beginning of ‘Isha’." He said: "And I think that as well."