Anyone who has read anything about the New Perspectives on Paul will realize that one of the key arguments is that we have misunderstood the Pharisees through the perspective of the Reformation. The first century Jews were never legalists, we are told. There are a number of problems with that position. The first is looking at Jesus' own perspective on the Pharisees seen most prominently in Luke 18. The second is that while we should acknowledge that the original message of the OT was one of grace, even if the official documents of the first century do indeed point to grace, that does not mean that grace was what was practiced. John Piper explains this further:

"Legalism may also exist in practice, even if grace is trumpeted in theory. Religionists may easily proclaim the primacy of grace and actually live as if the determining factor was human effort. The history of the Christian church amply demonstrates that a theology of grace does not preclude legalism in practice. It would be surprising if Judaism did not suffer from the same problem. Legalism threatens even those who hold to a theology of grace since pride and self-boasting are deeply rooted in human nature. . . ."

"Theology . . . is not measured only by formal statements but also by what it stresses. Any theology that claims to stress God's grace but rarely mentions it and that elaborates human responsibility in detail inevitably becomes legalistic in practice, if not theory." (Schreiner, Law and Its Fulfillment, pp. 115–116, cited in John Piper, The Future of Justification, p. 147.)