The word “heart” in both testaments…

In modern usage “heart” connotes primarily matters of the emotions or affections, and while that is a part of the biblical definition, it is not at all the whole picture.

The word “heart” in both testaments generally refers to the whole of man’s soul and all of its faculties as they are focused together upon something, whether good or evil.

Philip Lancaster, from Family Man, Family Leader, p. 137

The beatitudes concentrates on the heart…

The Sermon on the Mount, from which the beatitudes are taken, repeatedly concentrates on the “heart”—which referred to the deepest and central reality of the person (not merely the emotional center).

Douglas Groothuis, from On Jesus, p. 66