The Prophet (peace be upon him) taught several: reciting Ayat al-Kursi, upon which a guardian from Allah remains with you and no devil approaches until morning; and cupping the hands, reciting Surah al-Ikhlas, al-Falaq and al-Nas, then blowing into them and wiping over the body three times. He also said before sleeping, "Bismika Allahumma amutu wa ahya" (In Your name, O Allah, I die and I live). And he taught Fatimah to say SubhanAllah 33 times, al-Hamdulillah 33 times, and Allahu Akbar 34 times, saying it is better for them than a servant.
Evidence — the daleel
Sahih al-Bukhari 2311 ṢaḥīḥSahih al-Bukhari 5017 ṢaḥīḥSahih al-Bukhari 6324 ṢaḥīḥSahih al-Bukhari 3705 Ṣaḥīḥ
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.