Of things that are desirable for a Muslim to recite when going to sleep is Surat Al Kafirun and making it the last Surah to recite before sleep because it is an acquittal of polytheism.
Imam Ahmad reported in his Musnad on the authority of Farwah ibn Nawfal Al Ashja`y from his father (may Allah be pleased with him) that he said: "The Prophet (peace be upon him) gave me the daughter of Um Salamah and said: "You are my wet nurse. He said: I went for a long time then I came to him. He (the Messenger) said: What did the slave girl do? He said: She is at her mother. He asked: Why did you come? I said: I came to learn what to say upon sleeping. He (the Messenger) said: Recite Surat Al Kafrun upon your sleep because it is an acquittal of polytheism." [Al Musnad (5/456) and Al Albany (may Allah bestow mercy upon his soul) graded it as authentic in Sahih At-Targhib (No. 604)].
The Hadith shows the virtue of this Surah and the virtue of reciting it before going to sleep. It also exhorts Muslims to sleep after reciting it in order that the last words a person utters would be the declaration of monotheism which is an acquittal of polytheism. No doubt that whoever recites it, understands its meaning, and acts according to its teachings has acquitted himself from apparent and hidden polytheism. Some of the Pious Predecessors used to call it: "Al Muqashqishah." It is said: So and so Qashqasha i.e., was cured of his disease because the Ayah acquits a person from polytheism.
The Ayah along with Surat Al Ikhlas are called the two Surahs of Ikhlas because they contain the two types of monotheism: the scientific and the practical.
The Prophet (peace be upon him) used to recite these Ayahs in the two Rak`ahs of the Fajr Salah, beginning with them the actions of the day. He also used to recite them in the supererogatory Salah of Al Maghrib to conclude the actions of the day. And He used to recite them in Witr Salah (prayer of odd number Rak`ahs) to conclude the actions of the night. We have previously mentioned that the Prophet (peace be upon him) used to recite Surat Al Ikhlas upon going to sleep. The Hadith of Nawfal exhorts Muslims to recite Surat Al Kafirun upon going to sleep in order to conclude the action of the whole day.