Chapter 50: The Book of Seeking Refuge with Allah
It was narrated from Mu' adh bin 'Abdullah that his father said: "It was raining and dark, and we were waiting for the Messenger of Allah [SAW] to lead us in prayer. Then the Messenger of Allah [SAW] came out to lead us in prayer and he said: 'Say.' I said: 'What should I say?' He said: 'Say: He is Allah, (the) One and Al-Mu' awwadhatain in the evening and in the morning, three times, and that will suffice you against everything.'"
Sunan an-Nasa'i 5428