In Matthew 5:17, Jesus states that he has not come to abolish the law, but to fulfill it.
However, much of the law written in Deuteronomy is not practiced by Christian churches today (Deut 22:11 is a good example, forbidding the wearing of garments that mix linen and wool). I have heard this explained that the new covenant of Christ overrides the old covenant of law, but I can't find a clear scriptural basis for this idea.
Further, it would appear to me that in the cases where Jesus rebuked the Pharisees, such as in Matthew 12:10 in healing a man with a withered hand on the Sabbath, he was not critical of the law of keeping the Sabbath holy, but the Pharisees' incorrect interpretation of that law.
