When someone wants to discredit the Bible's testimony, a common challenge is, "Why don't you stop eating shellfish?!"  Sadly, many Christians don't know how to handle this objection, though they know deep down that there's a reason they've set aside Old Testament ceremonies.  The ancient, biblical way of explaining this is by recognizing the Threefold Division of the Mosaic Covenant: (1) moral law, (2) civil law, and (3) ceremonial law.  Moral law is a restatement of the law of nature, which was inscribed on man's heart in creation (Rom. 2:14-15; cf. Rom. 1:32).  Therefore, the abrogation of the Mosaic Covenant (Heb. 8:13) does not nullify the moral teaching found in the Old Testament.  It does, however, nullify the direct application of civil (associated with Elders, Judges, and Kings) and ceremonial law (associated with Priests, worship, and the holy place).  Christ has come as the fulfillment of the law and inaugurated a better covenant.