Summary, Lines 1-4 Edit
This sura asks for protection from various evils, such as the dark of the night, or the "envies" of the "envious". In verse 4, "those who blow on knots" refers to would-be witches. According to Abdullah Yusuf Ali, in the time of the Islamic prophet Muhammad, some "women of a tribe would try to cast spells on enemies by tying a knot in rope and reciting spells and blowing on them". The "evil of the envious when he envies" is taken by some to allude to the evil eye, although it can equally well be taken literally.
Al-Falaq and Surah Al-Nas are together termed the Al-Mu'awwidhatayn, or 'Surahs of Refuge'; they deal with roughly the same theme and form a natural pair. There is a Sunnah, or tradition of Muhammad, of reading it over the sick or before sleeping.