Musnad Ahmad 30:1759

Ishaq narrated to us, Malik informed us, from Suhayl, from his father, from Abu Hurayrah, that a man from Aslam said: "I did not sleep this night; a scorpion stung me." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Had you said when you entered the evening: 'I seek refuge in the perfect words of Allah from the evil of what He created,' it would not have harmed you."