To unite people on the basis of “fitra”, that is, the natural order established by God. That is indeed the religion sent down to prophets from Adam (PBUH) to Muhammad (PBUH) with the same fundamental principles:
“So set your face duly and steadily to that religion, the rules that apply to all beings (the fitra) set by God. He has created humankind in compliance with it. There is nothing to substitute what God creates. That is the upright religion, but most people do not know.
Set your face directly to this religion, the natural order (fitra) set by God. He has created mankind in compliance with it. There is nothing to replace that which God has created. That is the upright religion, but most people do not know.”” (Rum 30:30)
“The religion in the sight of God is Islam.” (Al e Imran 3:19)