What is Iman

One day the Messenger of Allah (ﷺ) appeared before the public that a man came to him and said: Prophet of Allah, (tell me) what is Iman. Upon this he (the Holy Prophet ﷺ) replied:
That you affirm your faith in Allah, His angels, His Books, His meeting, His Messengers and that you affirm your faith in the Resurrection hereafter.

-Sahih Muslim: Book 1,Hadith 5

Sahih Muslim, B1, H5