Reference: Fataawa Noor ‘alad-Darb – Question No.6316, Page 154, Volume 12
Question: What is the best supplication which is recommended to oft-repeat?
Response: The best and all-encompassing supplication is His (Ta’aala) saying:
So this is the most encompassing of supplications, because it combines the best of both this world and the Hereafter.
And the Messenger of Allaah (sal-Allaahu ‘alayhi wa sallam) used to supplicate with this a lot, so you should supplicate with this supplication, and likewise with [all the other] legislated supplications – just so as to practice the Sunnah from all aspects.