Chovos Halvavos explains another reason why the duties of the heart demand serious study. Physical mitzvos are defined and countable — but the obligations of our minds and hearts have no such limits.

As Dovid Hamelech tells us, “To every goal I have seen an end, but Your commandment is exceedingly broad.” The more we understand the inner service of Hashem, the more we discover that there is always another level.