I have heard one Scholar say the following:
“Reciting the three Quls three times [each] in the morning and evening is weak, and what’s preserved is one time [each] without [reciting]: Qul huwallahu Ahad. Only recite Surah Nas and Surah Falaq.”
In my view, this is incorrect. The Hadith that encourages the recital of the three ‘Quls’ every morning and evening is authentic. See below.
Sayyiduna ‘Abdullah ibn Khubayb (radiyallahu’anhu) reports that Rasulullah (sallallahu’alayhi wasallam) said: ‘…Recite Qul huwallahu Ahad, Qul A’udhu bi Rabbil Falaq and Qul A’udhu bi Rabbin Nas, thrice every morning and evening. It will suffice you for everything.’
(Sunan Abi Dawud, Hadith: 5041 and Sunan Tirmidhi, Hadith: 3575)
Imam Tirmidhi (rahimahullah) has declared this Hadith authentic (Hasan Sahih Gharib) . ‘Allamah Nawawi (rahimahullah) has also declared it authentic (sahih).
Refer: Al-Adhkar, Hadith: 216.
And Allah Ta’ala Knows best,
Answered by: Moulana Muhammad Abasoomar