The Old Testament is full of rules and regulations. All those rules were meant to maintain Israel as a chosen people with a shining holiness, a special relationship with God. Their holiness was not just for their own personal good, but it was also supposed to attract others to God.
Over time, many in Israel forgot the reason for the rules and the rules became nothing more that rigid, external customs of formalities. It is much easier to obey an external rule than to change our heart and soul. Their relationship with God and neighbor, their holiness, became nothing more than a rigid living out of rules.
In today’s Gospel Jesus points out to his host that the Pharisees’ hearts are full of plunder and evil. Plunder comes from taking by force something from another person. They really did not have a good, holy relationship with their neighbors. And, of course, evil intentions in the heart separated them from God.
Rather than concentrating on external practices of purity or holiness, Jesus calls them and us to give away what we have put in our hearts. That will leave only God in our hearts and make us truly holy and clean.
But as to what is within, give alms,
and behold, everything will be clean for you.