"I tell you, something greater than the temple is here. And if you had known what this means, I desire mercy, and not sacrifice,’ you would not have condemned the guiltless. For the Son of Man is lord of the Sabbath.”
Blind adherence to religious rules made the Pharisees miss the meaning of mercy and grace. It set them as enemies of Jesus. It ruined them for real worship because it is humbling to appeal to God's mercies to sinners rather than demanding acknowledgement for our efforts. And it is ironic that it took God in the flesh Who is perfect, sinless, and holy to truly demonstrate to the sanctimonious Pharisees what it takes to truly know and receive mercy. Yet as Lord of the Sabbath, Jesus did so.
There is bound up in the human heart an awful tendency to attempt to steal God's glory. We want to take credit for ourselves. We want our accomplishments to impress God. We are taken with our own achievements, ignoring all the bad with which we have infused even the best actions we've taken or thoughts we have had. But the truth is that we are born in sin and all our righteous acts are the filthiest of garbage to God.
I need mercy and grace to be given to me. Mercy is needed so that I do not get the consequences my sins deserve in judgment. Grace is needed so that my life might overflow with a goodness not my own. And in the truth of Jesus I find both for me. God is merciful to me a sinner, forgiving me through the atoning sacrifice of the Son of God. God is gracious to me, showering me with every blessing in Christ Jesus.