Al-Mu'awwidhatain

السلام عليكم و رحمة الله و بركاته بِسْمِ اللهِ الرَّحْمنِ الرَّحِيمِThe Messenger of Allah (صلى الله عليه و سلم ) used to seek protection against the evil of jinn and the evil eyes till Surat Al-Falaq and Surat An-Nas were revealed. After the were revealed, he took to them for seeking Allah's protection and left everything else besides them.[At-Tirmidi]
Commentary: These Surah are also called 'Al-Mu'awwidhatain' which mean two Surah which provide protection. It is, therefore very useful to seek the protection of Allah by reciting them.