Narrated AbuSalih Zakwan as-Samman: A man from Aslam tribe said: I was sitting with the Messenger of Allah (ﷺ). A man from among his Companions came and said: Messenger of Allah! I have been stung last night, and I could not sleep till morning. He asked: What was that? He replied: A scorpion. He said: Oh, had you said in the evening: "I take refuge in the perfect words of Allah from the evil of what He created," nothing would have harmed you, Allah willing.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا زُهَيْرٌ، حَدَّثَنَا سُهَيْلُ بْنُ أَبِي صَالِحٍ، عَنْ أَبِيهِ، قَالَ سَمِعْتُ رَجُلاً، مِنْ أَسْلَمَ قَالَ كُنْتُ جَالِسًا عِنْدَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَجَاءَ رَجُلٌ مِنْ أَصْحَابِهِ فَقَالَ يَا رَسُولَ اللَّهِ لُدِغْتُ اللَّيْلَةَ فَلَمْ أَنَمْ حَتَّى أَصْبَحْتُ . قَالَ " مَاذَا " . قَالَ عَقْرَبٌ . قَالَ " أَمَا إِنَّكَ لَوْ قُلْتَ حِينَ أَمْسَيْتَ أَعُوذُ بِكَلِمَاتِ اللَّهِ التَّامَّاتِ مِنْ شَرِّ مَا خَلَقَ لَمْ تَضُرَّكَ إِنْ شَاءَ اللَّهُ " .
sunnah.com