Jesus is still at it in today's Gospel, taking aim at the practices of the scribes and Pharisees (but not at their teachings). The homilist this morning made a very good point about the tendency of people who are committed to holiness of life to overemphasize the external. This can lead to a scrupulosity that loses track of what today's Gospel sums up as "justice, mercy and fidelity."
This is easy enough to understand: It's much easier to focus on things that are more within reach, and external things are under our control. After all, "justice, mercy and fidelity" are attributes of GOD! It can be overwhelming to keep these things in mind as my actual vocation. But in today's first reading, it is Paul who encourages us: God wants to strengthen our hearts for this very thing.