Say three times:

بِسْمِ اللَّهِ الَّذِيْ لَا يَضُرُّ مَعَ اسْمِهِ شَيْءٌ فِي الْأَرْضِ وَلَا فِي السَّمَاءِ وَهُوَ السَّمِيعُ الْعَلِيمُ

Bismillaahil-lathee laa yadhurru ma'as-mihi shay'un fil-'ardhi wa laa fis-samaa'i wa Huwas-Samee 'ul- 'Aleem.

In the name of Allah with whose name nothing is harmed on earth nor in the heavens and He is The All-Seeing, The All-Knowing. Uthman (RA) say: I heard the Messenger of Allah (ﷺ) say: If anyone says three times: "In the name of Allah, when Whose name is mentioned nothing on Earth or in Heaven can cause harm, and He is the Hearer, the Knower" he will not suffer sudden affliction till the morning, and if anyone says this in the morning, he will not suffer sudden affliction till the evening.

Reference: Sahih (Albani). Abu Dawud: 5088