The Messenger of Allah ﷺ said, "My eyes sleep, but my heart does not sleep."
حدثنا يحيى عن ابن عجلان قال سمعت أبي
قال رسول الله ﷺ تنام عيني ولا ينام قلبي
Its isnad is sahih. Bukhari related it, 4/232, in The Book of Virtues, "The Prophet's eyes would sleep," and Muslim, 1/509, no. 738, in The Book of the Prayer of Travelers, "The night prayer and the number of rak'ahs of the Prophet ﷺ," and Tirmidhi, 2/303, no. 439, in The Book of Prayer, "What has been said describing the Prophet's prayer," and Nasai, 3/234, no. 1698, in The Book of Night Prayer, "How the Witr is performed with three," and Ibn Khuzayma, 1/29, no. 48, and Ibn Hibban, 522, no. 2124.