Exegesis of the saying of Allah the Exalted: "And worship Allah and do not associate anything with Him." Why was the Messenger (peace and blessings be upon him) not mentioned?

The Shaykh : So He commanded and prohibited; He commanded worship and prohibited shirk (associating partners with Allah), and this means sincerity. Where is the right of the Messenger? Where is the testimony that Muhammad is the Messenger of Allah? A person might ask, for Allah mentioned His right, and then what? The right of the parents? We say: because the right of Allah is not completed except by fulfilling the right of the Messenger (peace and blessings be upon him), for worship necessarily requires following, and following is the implication of the testimony that Muhammad is the Messenger of Allah, is that not so, O people?
The student: Yes.

The Shaykh : So we say: the right of the Messenger (peace and blessings be upon him) is mentioned within His saying: because it is not possible for the worship of Allah to be completed except by following the Messenger (peace and blessings be upon him), and it is not possible to follow him except by testifying that he is the Messenger of Allah (peace and blessings be upon him), for the testimony that Muhammad is the Messenger of Allah is to believe in what he reported, to comply with what he commanded and prohibited, and not to worship Allah except with what He has prescribed.