[Scholarly Views on the Distinction Between Islam and Faith]
Some of them said: Faith consists of words and deeds, while Islam consists of doing what a person is obligated to do. This distinction applies when the two terms are mentioned together—as in “the believers and the Muslims”—each as a distinct designation: one conveys a meaning not conveyed by the other. But when either term is mentioned alone, it encompasses them all.
Many of them (1) said: Islam and faith are one and the same. Allah, the Almighty and Majestic, said:
“Whoever seeks a religion other than Islam, it will never be accepted from him.” [Āl ‘Imrān: 85]
If faith were something other than Islam, it would not be accepted from him. He also said:
“So We brought out whoever was there of the believers. But We found there only one household of Muslims.” [Al-Dhāriyāt: 35–36]