What to Say when Going to Sleep

Surely in the creation of the heavens and the earth, and the alternation of night and day (with their periods shortening and lengthening), there are signs (manifesting the truth) for the people of discernment. They remember and mention Allah (with their tongues and hearts), standing and sitting and lying down on their sides (whether during the Prayer or not) (Al Imran 3:190–191)

712. Abu Hurayra, may Allah be pleased with him, reported that the Messenger of Allah, peace and blessings be upon him, said, “When one of you retires to bed, he should wipe over his bed with the inside of his wrapper. He does not know what might have been on it after him. Then he should say, (By Your name, my Lord, I have lain on my side and I have raised it up by You. If You keep my soul, show mercy to it. If You release it, then protect it in the way You protect Your virtuous servants).” (Sahih al-Bukhari, Da’awat, 13; Sahih Muslim, Dhikr, 64).
Annotation: The warning at the beginning needs to be taken in terms of the conditions of the time (which can still be true while camping in a forest area). People lived in wooden houses without lighting system. Therefore it is so natural for the Prophet to advise both material and spiritual protection. As for today, houses are brightly lighted and relatively clear of insects. The first point to consider here is having the place to sleep cleared of things that can cause harm. And the second point is to recite the prayer mentioned and asking forgiveness from Allah.

713. Aisha, may Allah be pleased with her, reported that when the Messenger of Allah, peace and blessings be upon him, went to bed, he would recite the chapters Al-Ikhlas, Al-Falaq and An-Nas, blow into his hands, and wipe his body with them.” (Sahih al-Bukhari, Da’awat, 12).