'Amr bin Shu'aib narrated from his father, from his grandfather, that the Messenger of Allah ﷺ said: "When one of you becomes frightened during sleep, then let him say: 'I seek refuge in Allah’s Perfect Words from His anger, His punishment, and the evil of His creatures, from the whisperings of the Shayatin, and that they should come (A'udhu bikalimatillahit-tammati min ghaḍabihi wa 'iqabihi wa sharri 'ibadih, wa min hamazatish-shayaṭini wa an yaḥḍurun).’ For verily, they shall not harm him". He said: "So 'Abdullah bin 'Amr used to teach it to those of his children who attained maturity, and those of them who did not, he would write it on a sheet and then hang it around his neck".