One of the most frequent and toughest questions I get asked is how Christians are to treat the Mosaic Law. Why don’t we have to avoid wearing blended clothing or be circumcised or avoid eating shellfish?
G. K. Beale, in his A New Testament Biblical Theology, argues for what I believe is the correct answer to this question. The following is a lengthy quote (pp. 424-425), but I think it’s well worth reading (as is the entire book):
…Jesus redefines a true Israelite as ‘whoever does the will of my Father’ [Matt. 12:46-50]…. Jesus’ true family consists of those who trust in him, not those who are related to him by blood. Because Jesus is restoring not only Israel but also all of creation, including gentiles (Matt. 15:21-28; 21:40-44), the true people of God no longer can be marked out by certain nationalistic badges that distinguish one nation from another. … Jesus is redefining the true Israel, the true people of God, by saying that loyalty to him is the mark of a faithful Israelite. People no longer must possess the badges of old national Israel in order to be part of the true, new Israel. … You do not have to be of the bloodline of Abraham to be his true child, nor do you have to move to Israel geographically to become an Israelite; you merely have to move to Jesus, true Israel, and embrace him. As we will see, this applies to the temple (Jesus is the temple), circumcision (in him we have been circumcised [Col. 2:11]), and the Sabbath rest (true ultimate rest is found in him forever, not merely physical rest on the seventh day).
In other words, the Mosaic Law served as a covenant boundary marker around ethnic Israel, but now Jesus as true Israel serves as the covenant boundary marker around spiritual Israel (as Beale notes [p. 425, n. 93], this was argued previously by, among others, N. T. Wright in Jesus and the Victory of God [401-403]).