Shaykh ul-Islaam Ibn Taymiyyah (d.728 A.H.) – Rahimullaah – said:
‘Know that it is obligatory upon every mature, intelligent person from mankind and the Jinn to testify that none has the right to be worshipped except Allah, and that Muhammad is His slave and Messenger.
Allah sent him with the guidance and the religion of the truth to make it uppermost above all religions, and Allah is sufficient as a witness. Allah sent him to all of creation, mankind and Jinn, the Arabs and the non-Arabs, the Persians and the Indians, the Barbars and the Romans, and all the different types of non-Arabs, black and white. What is meant by non-Arabs is those who do not have the Arab language, amongst all their different languages.
So Muhammad – sallallaahu alayhi wa sallam – was sent for every single person from the humans and the Jinn, whether they are from those who follow a revealed Book or not. He was sent for every single person in relation to his Deen, from the inward matters and outward ones, regarding his beliefs, realities, methods and his legislations.
So there is no ‘Aqeedah (belief) except the Messenger’s – sallallaahu alayhi wa sallam – ‘Aqeedah, and there is no reality except his reality, and there is no method except his method, and there is no legislation/Sharee’ah except his Sharee’ah/legislation.
No one from the creation can reach to Allah, and to His pleasure, and His Paradise, and to His Generosity, and His Guardianship except by following the Messenger – sallallaahu alayhi wa sallam – inwardly and outwardly, and in sayings and actions inwardly and outwardly, in statements of the heart and its beliefs, and the conditions of the heart and its realities, and the statements of the tongue and the actions of the limbs.’
Taken from: ‘Majmoo’ Fatawa’ 10/430-431 – Translated by Abbas Abu Yahya