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Takhrij Hadith 962: "The Prophet, peace and blessings…"
Farwah ibn Nawfal al-Ashja‘i narrated from his father, who said:
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The Prophet, peace and blessings be upon him, entrusted to me the daughter of Umm Salamah and said: “You are only her foster father”. I remained for as long as Allah willed, then I came to him. He asked: “How is the young girl?” — or he said: “the little girl?” I replied: “She is with her mother”. He said: “Then why have you come?” I replied: “Teach me what I should say before going to sleep”. He said: “Recite {Say: O disbelievers}[Surah al-Kafirun] before going to sleep, then sleep after completing it, for it is a declaration of freedom from shirk (polytheism)”.”