Thomas Aquinas, Commentary on Romans 3 . 4 . 321
Then when [the Apostle Paul] says, “Do we then destroy the law?” he excludes an objection. For someone might claim that he is overthrowing the . . . law; therefore, he asks: “Do we then destroy the law through faith?” inasmuch as we say that men are justified without the works of the law? He answers: “God forbid!” in keeping with Matthew, “Not an iota, not a dot, will pass from the law” (Matt. 5:18). Rather, he adds: “we uphold the law,” i.e., by faith we complete and fulfill the Law, as Matthew says, “I have come not to abolish the law but to fulfill it” (Matt. 5:17). This is true as regards the ceremonial precepts because, being figures, they were upheld and fulfilled by the fact that the truth signified by them is shown forth in the faith of Christ.
Thomas Aquinas, Commentary on Romans 3.4.321
What Paul sees happening in Christ and in the Christian Church, like what Jesus had said in Matthew, is the fulfillment and not the abolition of the meaning of Torah as covenant of grace. “Fulfillment” is a permanently open border between what went before and what comes next.
John Howard Yoder, The Jewish-Christian Schism Revisited