"Woe to you, scribes and Pharisees, hypocrites! For you tithe mint and dill and cummin, and have neglected the weightier provisions of the law: justice and mercy and faithfulness; but these are the things you should have done without neglecting the others" (Mt. 23:23).
Jesus mentions two ways in which one might serve God. One way is to take the larger principles (justice, mercy, faithfulness) and go through life trying to live by those principles. The other way is to pay close attention to the smallest detail (tithing of herbs), no matter how insignificant it may seem to others.
Some have tried to take this verse and say we must choose whether we will serve God through right principles or through following the strictest details. Actually, Jesus says we must do both - "these are the things you should have done [concepts of justice, mercy, and faithfulness] without neglecting the others [carefulness of strict adherence to the Law]."
The Pharisees were condemned by Jesus for many things. As a result, it is sometimes easy to associate everything about the Pharisees as being wrong. But the Pharisees were NOT condemned for trying to strictly adhere to the Law in this instance. Their strict adherence did not cause them to neglect the "weightier provisions" either. They were just negligent in these areas and needed to be corrected.
So what is the point of the verse? Not that we must choose to focus on principles and attitudes OR precepts and actions. But that we must strive to strictly follow all of the Lord's commands while allowing our hearts and minds to be guided by the greater concepts of the gospel of Christ.