One of the most common mistakes people make with the Bible, is to confuse the issues of Law and grace. The Scriptures make the difference when they say "The Law came by Moses, but grace and truth came by Jesus Christ." The Law of Moses is categorized into three parts: the Moral Law (the 10 Commandments), the Civil Law (the Law for Israel's court system) and the Ceremonial Law (the Law for ceremonial worship). The whole Law had 613 precepts (its do's and don'ts ).
Male circumcision was part of the ceremonial Law given to Israel to set them apart from other nations, as was not eating pork and Sabbath worship. Capital punishment under the Law--for murder, adultery, idolatry, blasphemy was part of the civil Law of Israel, so why should we as a nation live under the standards of justice given to a nation three thousand years ago? We are under no obligation to keep any of the dietary, civil, or ceremonial Laws of Israel.
However, we are under obligation to keep the Moral Law. It was given to Israel but its purpose is to "leave the whole world guilty before God" (see Romans 3:19-20). And it certainly does. When we study its holy precepts and understand that we violate the Seventh by our lust, it shows us we need the grace (mercy) of God.
The reason the Moral Law leaves us guilty before God is that its precepts are written on our hearts, via the conscience. We intuitively know that its wrong to lie, to steal, to lust, to hate, to murder, to commit adultery, etc.
It was one night way back in 1972 that the Law showed me that I was guilty, heading for Hell, and it sent me to the Savior where I found mercy. The Law came by Moses, but grace and truth came by Jesus Christ. As the hymn-writer wrote 200 years ago:
"By God's grace at last my sin I learned, then I trembled at the Law I spurned, till my guilty soul imploring turned, to Calvary."