Sayyiduna Abu Umamah (may Allah be pleased with him) narrates: We were with the Messenger of Allah (peace and blessings be upon him) on a journey, and the Messenger of Allah (peace and blessings be upon him) did not wake from sleep until the heat of the sun troubled him between his shoulders. When he (peace and blessings be upon him) woke, the people waited for a while; then he (peace and blessings be upon him) had the prayer called, stepped forward and led them in prayer. When he had finished leading the prayer, he said: "When one of you falls asleep and his eyes overcome him, let him do likewise, for Allah takes the souls at the time of their death, and the one that does not die He takes (temporarily) in its sleep."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7942