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.'"