Jami` at-Tirmidhi Book 48, Hadith 205
“When you go to your bed, perform the Wudu’ as you would perform for Salat. Then lie on your right side, then say: ‘O Allah, I submit my face to You, and I entrust my affair to You, and I lay myself down relying upon You, hoping in You and fearing You. There is no refuge nor escape from You except to You. I believe in Your Book which You have revealed, and in Your Prophet whom You have sent (Allāhumma aslamtu wajhī ilaika wa fawwaḍtu amrī ilaika, wa alja’tu ẓahrī ilaika, raghbatan wa rahbatan ilaika, lā malja’a wa lā manjā minka illā ilaika, āmantu bikitābikalladhī anzalta wa bi-nabiyykalladhī arsalt).’ And if you die that night, you shall die upon the Fitrah” - Al-Bara’ said: I repeated it to retain it in memory, “So I said: ‘I believe in Your Messenger whom You have sent.’” He said: “So he (ﷺ) struck with his hand upon my chest, then said: ‘And in Your Prophet whom You have sent.’”
“There is not a Muslim upon the earth who calls upon Allah with any supplication, except that Allah grants it to him, or he turns away from him the like of it in evil; as long as he does not supplicate for something sinful, or the severing of the ties of kinship.” So a man from the people said: “What if we should increase (in it)” He (ﷺ) said: “(With) Allah is more.”
“We went out on a rainy and extremely dark night, looking for the Messenger of Allah (ﷺ), so that he could lead us in Salat.” He said: “So I met him and he (ﷺ) said: ‘Speak’ but I did not say anything. Then he (ﷺ) said: ‘Speak.’ But I did not say anything. He (ﷺ) said: ‘Speak.’ So I said: ‘What should I say?’ He (ﷺ) said: ‘Say: “Say: He is Allah, the One” and Al-Mu`awwidhatain, when you reach evening, and when you reach morning, three times, they will suffice you against everything.’”