Dua for Protection from Harm
'Uthmaan bin 'Affaan (Radhi Allah Anh) said: Prophet Muhammad (Sal Allahu 'Alayhi Wa Sallam) said, "Whoever recites this three times in the morning will not be afflicted by any calamity before evening, and whoever recites this three times in the evening will not be afflicted by any calamity before morning."
بِسْمِ اللّٰهِ الَّذِي لَا يَضُرُّ مَعَ اسْمِهِ شَيْءٌ فِي الأَرْضِ وَلَا فِي السَّمَاءِ وَهُوَ السَّمِيعُ الْعَلِيمُ
Bismillaahil-ladhee laa yadhurru ma'as-mihi shayun fil-ardhi wa laa fis-samaai, wa Huwas-Samee-'ul-'Aleem
In the Name of Allah with Whose Name nothing can cause harm in the earth or in the heavens, and He is the All-Hearing, the All-Knowing.
[Abu-Dawood and At-Tirmidhi]