Muhammad followed Milat Ibrahim

Prophet Muhammad was given God's final scripture, which contains the final book of law for mankind. Yet, all of the religious practices (manasak) that make up the religion of Submission (Islam) came from Abraham. This is why God consistently commands Muhammad to follow the religion of Abraham (millet Ibrahim).

[16:123] Then we inspired you (Muhammad) to follow the religion of Abraham, the monotheist; he never was an idol worshiper.

ثُمَّ أَوْحَيْنَا إِلَيْكَ أَنِ اتَّبِعْ مِلَّةَ إِبْرَاهِيمَ حَنِيفًا وَمَا كَانَ مِنَ الْمُشْرِكِينَ

Abraham was explicitly taught how to perform the Salat.

[21:73] We made them imams who guided in accordance with our commandments, and we taught them how to work righteousness, and how to observe the Contact Prayers (Salat) and the obligatory charity (Zakat). To us, they were devoted worshipers.

وَجَعَلْنَـٰهُمْ أَئِمَّةً يَهْدُونَ بِأَمْرِنَا وَأَوْحَيْنَآ إِلَيْهِمْ فِعْلَ ٱلْخَيْرَٰتِ وَإِقَامَ ٱلصَّلَوٰةِ وَإِيتَآءَ ٱلزَّكَوٰةِ وَكَانُوا۟ لَنَا عَـٰبِدِينَ

Part of the Salat is reciting the Shahadah. If the Salat came from Abraham and Muhammad was commanded to follow the religion of Abraham, it does not make sense that Abraham would have had Muhammad's name in his Shahdah. Nor does it make sense that Muhammad would have commanded the people to insert his own name in the Salat.

[3:79] Never would a human being whom GOD blessed with the scripture and prophethood say to the people, "Idolize me beside GOD." Instead, (he would say), "Devote yourselves absolutely to your Lord alone," according to the scripture you preach and the teachings you learn.

(٧٩) مَا كَانَ لِبَشَرٍ أَن يُؤْتِيَهُ ٱللَّهُ ٱلْكِتَـٰبَ وَٱلْحُكْمَ وَٱلنُّبُوَّةَ ثُمَّ يَقُولَ لِلنَّاسِ كُونُوا۟ عِبَادًا لِّى مِن دُونِ ٱللَّهِ وَلَـٰكِن كُونُوا۟ رَبَّـٰنِيِّـۧنَ بِمَا كُنتُمْ تُعَلِّمُونَ ٱلْكِتَـٰبَ وَبِمَا كُنتُمْ تَدْرُسُونَ