For Protection From Harm
بِسْمِ اللَّهِ الَّذِي لَا يَضُرُّ مَعَ اسْمِهِ شَيْءٌ فِي الْأَرْضِ وَلَا فِي السَّمَاءِ، وَهُوَ السَّمِيعُ الْعَلِيمُ
Bismillāhilladhī lā yaḍurru maʿa-smihi shayʾun fil-arḍi wa lā fis-samāʾi, wa Huwas-Samīʿul-ʿAlīm.
In the name of Allah, with whose name nothing on earth or in the heavens can cause harm, and He is the All-Hearing, All-Knowing.
Source: Hisnul Muslim #85