Musnad Ahmad 1251:0

Narrated to us by Yahya ibn Sa’id, from Ibn ‘Ajlan, who said: Zayd ibn Aslam narrated to me, from Ibn Wa’lah, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "Whoever says when he reaches his evening: 'I seek refuge in the perfect words of Allah from the evil of what He created' (A’udhu bi-kalimatillah al-tammati min sharri ma khalaq), no harm shall afflict him that night." Ibn ‘Ajlan said: Our people learned it and used to say it every night. One of them was stung by a scorpion, and it was said to him: "Did you not say it?" He replied: "I forgot to say it that night."