Musnad Ahmad 32:1126

Yazid ibn Harun narrated to us, Humayd informed us, from Anas ibn Malik, who said: It was asked, "Did the Messenger of Allah, may Allah bless him and grant him peace, make a ring?" He said: "Yes." He delayed the night prayer (Isha) until the middle of the night, then he prayed. When he had prayed, he turned with his face and said: "Indeed, the people have prayed and slept, and you have remained in prayer as long as you were waiting for the prayer." He said: It is as if I am looking at the glitter of his ring.