13 But go and learn what is the meaning of this; I desire mercy and not sacrifice, for I have not come to call the righteous, but sinners. Matthew 9:13 (translated from the NA28 Greek text)
Works righteousness is man’s default religion. The Jews mostly misunderstood the Old Testament sacrificial system. The point of the sacrifice was the taking away of sin and the pointing to the perfect sacrifice that would come in Christ, but most had turned it into a form of works righteousness.
In Matthew 9:13 (above) our Lord Jesus quotes Hosea 6:6.
6 For I delight in loyalty rather than sacrifice, And in the knowledge of God rather than burnt offerings. Hosea 6:6 (NASB)