So if they dispute with you (O Muhammad صلى الله عليه وسلم ) say: "I have submitted myself to Allah (in Islam), and (so have) those who follow me." And say to those who were given the Scripture (Jews and Christians) and to those who are illiterates (Arab pagans): "Do you (also) submit yourselves (to Allah in Islam)?" If they do, they are rightly guided; but if they turn away, your duty is only to convey the Message; and Allah is All-Seer of (His) slaves
Surah (Chapter) Al-e-'Imran(The Family of 'Imran) 3:20
It clearly implies that Muslims, in all walks of their lives, have to follow the traditions of the last Messenger of Allah, Muhammadصلى الله عليه وسلم. It is further reinforced by the following Hadith (Saying of Muhammad صلى الله عليه وسلم).
It is obligatory to have Belief in the Messengership of the Prophet (Muhammad صلى الله عليه وسلم ). Narrated Abu Hurairah رضي الله عنه : Allâh’s Messenger صلى الله عليه وسلم said: "By Him (Allah) in Whose Hand Muhammad’s soul is, there is none from amongst the Jews and the Christians (of these present nations) who hears about me and then dies without believing in the Message with which I have been sent (i.e. Islâmic Monotheism), but he will be from the dwellers of the (Hell) Fire." (Sahih Muslim , the Book of Faith, Vol.1, Hadith No.240).
Obeying the Messenger of Allah, Muhammad صلى الله عليه is like obeying Allah (God).
O you who believe! Obey Allah and obey the Messenger (Muhammad صلى الله عليه وسلم), and those of you (Muslims) who are in authority. (And) if you differ in anything amongst yourselves, refer it to Allah and His Messenger (صلى الله عليه وسلم), if you believe in Allah and in the Last Day. That is better and more suitable for final determination.
Surah (Chapter) an-Nisa"(The Women) 4:59
Following the Messenger of Allah, Muhammad صلى الله عليه is like loving Allah (God).
Say (O Muhammad صلى الله عليه وسلم to mankind): "If you (really) love Allah then follow me (i.e. accept Islâmic Monotheism, follow the Qur-an and the Sunnah), Allah will love you and forgive you your sins. And Allah is Oft-Forgiving, Most Merciful."
Surah (Chapter) Al-e-'Imran(The Family of 'Imran) 3:31
These Ayat (Verses) clearly indicate that only Allah (God) and His last Messenger, Muhammadصلى الله عليه وسلم are to be obeyed in all matters of religion.