Musnad Ahmad 27:1433

Surayj narrated to us, Hammad ibn Salamah narrated to us, from Ayyub, from Nafi’ and Bakr ibn ‘Abdullah, from Ibn ‘Umar: "That the Messenger of Allah (peace and blessings of Allah be upon him) prayed Dhuhr, ‘Asr, Maghrib, and ‘Isha’—meaning at al-Muhassab. Then he slept a light sleep, then he entered and performed Tawaf around the House."