The claim that Jews lost the covenant because they were not worthy of it is simply works-righteousness. Works-righteousness takes a gift provided by the free and unconditional grace of God and turns it into a condition apart from which God is not free to be gracious. Works-righteousness has nothing to do with an entirely different matter, the question of whether we are to do works of love toward the neighbor. With regard to the covenant, works-righteousness contends that God is not free to covenant with whomever God pleases but only with those who deserve to receive it. It claims that we deserve it, Jews do not. Christian anti-Judaism reflects a reward and punishment mind-set. Jews are punished by losing the covenant; we are rewarded with receiving it because we deserve it.
That’s from Clark Williamson’s A Guest in the House of Israel (pp. 113-114), tracing the development of Christian anti-Judaism. I plan to write more about this very challenging book soon.