THE DISTINCTION BETWEEN IMAN AND ISLAM

Lexically Iman signifies the acceptance and confirmation of something with one's heart, while Islam signifies obedience and submission. Iman pertains to the heart; so does Islam, but it is related to all the other parts of the human body as well. From the point of view of the Shariah, however, Iman is not valid without Islam, nor Islam without Iman. In other words, it is not enough to have faith in Allah and the Holy Prophet ﷺ in one's heart unless the tongue expresses the faith and also affirms one's allegiance and submission. Similarly, an oral declaration of faith and allegiance is not valid unless one has faith in one's heart.

From Ma'ariful Quran, Interpretation of Surah Al-Baqarah, by Mufti Muhammad Shafi RE