The Greatest of Manners
Shaikh Ibn Bāz, may Allāh have mercy on him, said:
This is what is the root of noble manners, its foundation, the greatest of them, and most obligatory of them: tawḥīd of Allāh,¹ ikhlāṣ for Him,² and abandoning all acts of shirk³ with Him.
Then following that are the five prayers; they are the greatest of manners and most important of them after tawḥīd and abandoning all acts of shirk³ with Allāh, all perfect is He and all high.
¹singling Him out in worship and everything that is His alone
²seeking only His pleasure and His reward in the Hereafter
³treating other than Allāh as an equal of His in something that is only His
N.B.: Title mine (Trans.)