Sunan Ibn Majah, Chapter: The Book of the Prayer

"Anas bin Malik was asked: 'Did the Prophet (saw) wear a ring?' He said: 'Yes.' One night he delayed the Isha prayer until almost the middle of the night. When he had prayed he turned to face us and said: 'The people have prayed and gone to sleep, but you will still be in a state of prayer so long as you are waiting for the (next) prayer.'" (Sahih) Anas said: "It is as if I can see the sparkle from his ring."