Musnad Ahmad 32:1019

Muhammad ibn Abdullah narrated to us, Humayd narrated to us, he said: Anas was asked, "Did the Prophet, may Allah bless him and grant him peace, take a ring?" He said: "Yes. One night he delayed the night prayer (al-Isha al-Akhirah) until near the middle of the night. When he prayed, he turned his face toward us and said: 'The people have prayed and slept, but you have remained in prayer as long as you were waiting for it.' Anas said: It is as if I am looking at the glitter of his ring right now."