Abu Hurairah reported,

The Messenger of Allah ﷺ said to me, "What did your captive do last night?"I replied, "Messenger of Allah, he claimed he would teach me words by which Allah would benefit me, so I let him go."He asked, "What were they?"I said, "He told me, 'When you go to your bed, recite Ayat al-Kursi from its beginning to its end, "Allah, there is no deity except Him, the Ever-Living, the Sustainer of existence" [Baqarah 2:255].' And he said to me, 'A protector from Allah will remain with you, and no devil will come near you until morning.'" The companions were the most eager of people for goodness.The Prophet ﷺ said, "He told you the truth, though he is a great liar. Do you know whom you have been speaking with these past three nights, Abu Hurayrah?"He said, "No."He said, "That was a devil."

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عن أبي هريرة قال

قال لي رسول الله ﷺ: ما فعل أسيرك البارحة؟ قلت: يا رسول الله زعم أنه يعلمني كلمات ينفعني الله بها فخليت سبيله قال: ما هي؟ قلت: قال لي إذا أويت إلى فراشك، فاقرأ آية الكرسي من أولها حتى تختم الآية {الله لا إله إلا هو الحي القيوم} وقال لي: لن يزال عليك من الله حافظ، ولا يقربك شيطان حتى تصبح، وكانوا أحرص شيء على الخير، فقال النبي ﷺ: أما إنه قد صدقك وهو كذوب، تعلم من تخاطب منذ ثلاث ليال يا أبا هريرة؟ قال: لا، قال: ذاك شيطان.