سنن النسائي

It was narrated that Ibn Shihaab said: "Humaid bin Abdur-Rahman bin 'Awf told me that a man from among the companions of the Prophet (ﷺ) said: 'I said, when I was on a journey with the Messenger of Allah (ﷺ): By Allah (SWT), I am going to watch the prayer of the Messenger of Allah (ﷺ) and see what he does. When he prayed 'Isha, he lay down for a long time. Then he woke up and looked toward the horizon and said: "Our Lord! You have not created (all) this without purpose" until he reached: "for You never break (Your) Promise." Then the Messenger of Allah (ﷺ) reached across his bed and took a siwak from it, then he poured water from a vessel and cleaned his teeth. Then he stood and prayed until I said: He has prayed for as long as he has slept. Then he lay down until I said: He has slept as long as he prayed. Then he woke up and did the same as he had done the first time and said the same as he had said. The Messenger of Allah (ﷺ) did that three times before Fajr.'"