What is the difference between faith as a statement and action, and faith as an act of the heart, and which of them increases and decreases, with supporting evidence?

"Faith" may refer to the root of faith in the heart, which is affirmation and love. It may also refer to its complete reality, encompassing the saying and action of the heart, the saying of the tongue, and the actions of the limbs. If the root of faith disappears, the designation of "believer" is absolutely removed from its possessor, and this is what distinguishes a believer from a disbeliever. As for absolute, complete faith, it is denied to disobedient monotheists due to their failure to achieve complete faith, even if they possess the root of faith which will eventually allow them to exit the Fire. A man may be a Muslim but not a believer, meaning he possesses the root of faith without its obligatory reality. Faith increases and decreases, and it encompasses what is in the heart and the actions of the limbs.