Al-Bara' bin 'Azib (May Allah be pleased with them) said:
Messenger of Allah ﷺ asked me to recite whenever I go to bed: "Allahumma aslamtu nafsi ilaika, wa wajjahtu wajhi ilaika, wa fawwadtu amri ilaika, wal-ja'tu zahri ilaika, raghbatan wa rahbatan ilaika, la malja wa la manja minka illa ilaika. Amantu bikitabikal-ladhi anzalta, wa nabiyyikal-ladhi arsalta (O Allah! I have submitted myself to You, I have turned my face to You, entrusted my affairs to You; and committed my back to You out of desire for You and fear of You; expecting Your reward and fearing Your punishment). There is no refuge and no place of safety from You but with You. I believe in the Book You have revealed and in the Prophet You have sent." Messenger of Allah ﷺ said that if anyone recited these words and died that night, he would die in the true religion. In case he remains alive till morning, he will obtain good.

[Al-Bukhari and Muslim].

In another narration: He reported Messenger of Allah ﷺ as saying: "If you go to bed, perform the Salat Wudu', lie down on your right side and say [the above Du'a (supplication)] and let these words be your last".

السابع: عن أبي عمارة البراء بن عازب رضي الله عنهما قال : قال رسول الله ﷺ :
" يا فلان إذا أويت إلى فراشك فقل: اللهم أسلمت نفسي إليك، ووجهت وجهي إليك: وفوضت أمري إليك ، وألجأت ظهري إليك، رغبة ورهبة إليك، لا ملجأ ولا منجى منك إلا إليك ، آمنت بكتابك الذي أنزلت، ونبيك الذي أرسلت؛ فإنك إن مت من ليلتك مت على الفطرة، وإن أصبحت أصبت خيراً" ((متفق عليه)) .