Musnad Ahmad 32:937

Yahya narrated to us, from Humayd, who said: Anas was asked, "Did the Prophet, peace and blessings of Allah be upon him, take a ring?" He said: "Yes. He delayed the night prayer (Isha) until half of the night had passed, then he said: 'Indeed, the people have prayed and gone to sleep, but you have remained in a state of prayer as long as you were waiting for it.' And it is as if I am looking at the glitter of his ring."