That you not be a slave to anyone other than Him, and that you not worship except in accordance with the Shari'ah of faith (explaining that the oneness of worship requires sincerity and following the Prophet)

The Shaykh : For this reason, he said: "That you not be a slave to anyone other than Him". You must never be a slave to anyone other than Allah. Worship Allah. And know that a person may worship his own desires, and how common it is to worship one's desires. This includes concealing the truth to please people or speaking falsehood to please people. In reality, such a person has worshipped other than Allah and has not worshipped Allah. The one who worships Allah submits to Allah, even if others are hostile to him; he seeks the pleasure of Allah above all else. For this reason, he said:
"That you not be a slave to anyone other than Him, and that you not worship except in accordance with the Shari'ah of faith". The first part contains the requirement of sincerity, and the second part contains the requirement of following the Prophet.
"And that you not worship except in accordance with the Shari'ah of faith".