One should recite the three Quls (i.e. Surah Ikhlaas, Surah Falaq and Surah Naas) before retiring to bed every night.
عن عائشة رضى الله عنها أن النبى صلى الله عليه وسلم كان إذا أوى إلى فراشه كل ليلة جمع كفيه ثم نفث فيهما وقرأ فيهما (قل هو الله أحد) و ( قل أعوذ برب الفلق) و (قل أعوذ برب الناس) ثم يمسح بهما ما استطاع من جسده يبدأ بهما على رأسه ووجهه وما أقبل من جسده يفعل ذلك ثلاث مرات. (ابو داود رقم 5058)
Hadhrat Aaisha (Radhiallahu Anha) reports that whenever Rasulullah (Sallallahu Alaihi Wasallam) would retire to bed every night, he would recite Surah Ikhlaas, Surah Falaq and Surah Naas and thereafter blow on his both palms. Subsequently, he would rub his palms upon his entire body. He would commence rubbing his palms on his head, face and the front portion of his body. He would repeat this action three times.