Knowing what the Prophet (peace and blessings be upon him) was upon is a necessary concomitant of knowing the path upon which his Companions (may Allah be pleased with them) were.

The Shaykh : And among the necessary concomitants of this knowledge of what he (peace and blessings be upon him and his family) was upon is that we do not add anything to his worship, absolutely, due to the preceding verse regarding Allah (Mighty and Majestic) perfecting this religion and making it a great blessing upon this Ummah. For this reason, the Companions of the Prophet (peace and blessings be upon him and his family) knew this reality and did not add to what the Messenger of Allah (peace and blessings be upon him and his family) was upon of guidance and light. How so, when he (peace and blessings be upon him) was always, when he addressed them, saying at the beginning of his sermon, as you heard earlier at the beginning of this address:
And in a narration: Likewise, the statements of his Companions came from that, such as the saying of Abdullah ibn Mas'ud (may Allah be pleased with him): "Moderation in the Sunnah is better than exertion in religious innovation". Likewise, it was narrated from Hudhayfah ibn al-Yaman (may Allah be pleased with him) that he said: "Any act of worship that the Companions of the Messenger of Allah (peace and blessings be upon him and his family) did not perform, do not perform it". The reports and stories that came from the Salaf concerning standing by what came to us from the Messenger without adding to it are very numerous. So this amount of what we mentioned from the hadiths and reports is sufficient to clarify that what the Messenger (peace be upon him) was upon is what must be stood by and known, without adding to it, because we will not be able to encompass and perform all the acts of worship that the Messenger (peace and blessings be upon him) brought.