Hazrat Abu Saeed al-Khurdi (R.A) said:
“The Messenger (PBUH) of Allah used to seek refuge with Allah from the jinn and from the evil eye until the Mu’wadaitain (Surah Falaq and Surah Naas) were revealed, and whey they were revealed He started to recite them and not anything else.” (Tirmidhi)
It means that these two Chapters are great means of attaining shield from all kinds of evils present in this world.
In short, four Quls are very heavy in the magnitude of their benefits that they generate for the believers.
‘Sayyida A’isha (Allah be pleased with her) narrates: “Whenever the Messenger of Allah (Allah bless him & give him peace) would become ill, he would recite the Mu’awwizat (Surah al-Falaq & Surah an-Nas) and blow over himself. When his illness was aggravated, I used to recite these two Surahs (and blow my breath) over him and make him rub his body with his own hand, for its blessings.” [Sahih al-Bukhari, no. 4728]