Musannaf Ibn Abi Shayba 21:678

Jarir ibn Abd al-Hamid narrated to us, from Rafi’, from Abu Salih, who said: A man from the Ansar was stung. When morning came, he went to the Prophet, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, I remained awake all last night due to a scorpion sting." The Prophet, 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,' no scorpion would have harmed you until you reached the morning." Abu Salih said: So I taught it to my daughter and my son, and they were stung, but it did not harm them at all.