Musnad Ahmad 30:780

Yazid narrated to us, Hisham informed us, from Suhayl ibn Abi Salih, from his father, from Abu Hurayrah, who said: The Prophet (peace and blessings of Allah be upon him) said: "Whoever says when he enters the evening three times: 'I seek refuge in the perfect words of Allah from the evil of what He created,' no sting will harm him that night." He said: "Our family had learned it, so they used to say it. Then a slave girl among them was stung, but she did not feel any pain from it."