The letter of the law of Moses was that a man could give a bill of divorce to dimiss his wife. Jesus went beyond that to remind us that in the beginning it wasn't so, and that when a man leaves his mother and father to join with his wife, the two become one flesh, and therefore when a man divorces his wife and marries another or marries a divorced woman, commits adultery.

The Pharisees would have no problem with divorce and remarriage. Jesus on the other hand, told us this is adultery. What exactly is the "spirit" of thou shalt not commit adultery and Jesus' teaching as presented in His Gospel on this subject?