'The Religion of the Muslims is built upon...'‏‏

Shaykhul-Islam Ibn Taymiyyah (rahimahullaah) said:

"The Religion of the Muslims is built upon following the Book of Allaah, the Sunnah of His Prophet (sallallaahu ‘alayhi wa sallam) and that which the Ummah has agreed upon. So these are the three infallible usool (fundamentals).

So whatever the Ummah differs in, then it is referred back... to Allaah and His Messenger. Thus, it is not for anyone to set up a person for the Ummah, and to call to his way and form walaa’ (love, loyalty and allegiance) and ‘adaa (enmity and hatred) based upon that, except for the Prophet (sallallaahu ‘alayhi wa sallam). Nor is any speech set up for them based upon which they form walaa’ and ‘adaa except for the Speech of Allaah, and that of His Messenger, and that which the Ummah has agreed upon. Rather, this is that practice of the people of innovation, who set up a person or a saying, with which they cause splits in the Ummah; ..."

Majmoo‘ul Fataawaa (20/164)