... continued from Wednesday.
The problem is that the Scriptures inevitably have to be interpreted and, even once we interpret them, we constantly have to apply them to new kinds of situations. If the Law says, "you will not do any work on the Sabbath," then the next question is, "What exactly is work?" For example, how far would a person need to walk on the Sabbath before he or she had worked? Or does walking even fit in the category of work at all, or playing on a playground?
There is a certain personality that is driven to clarify these sorts of issues, to do away with ambiguities. If you tell me I must honor my father and mother, then what does that look like? What if my father is abusive? What if my mother is an alcoholic? It is always honoring to obey your parent? I don't want to disobey the commandment, so what exactly do I need to do in each circumstance?
If I am not to kill, then is capital punishment killing? What about war? Is killing in war a violation of the commandment? These are exactly the sorts of questions that the "traditions of the elders" tried to answer. Some Pharisees no doubt were strict because they wanted to make sure without a doubt that they were doing the right thing. Others no doubt enjoyed the rules a little too much and became legalists who lost sight of the point.
The kinds of personalities that are wired to answer these sorts of questions can be very helpful to us. They're the kinds of people we want to help us organize an event or keep our financial records. They're detailed people who can make the difference between a good idea that never happens and something great in the real world.
And we should not be too quick to criticize how many rules the Pharisees had. The Law in the Bible may have had 613 rules, according to popular count. But we have far more traffic rules. Does everyone in the car have to wear a seat belt? How far do I have to stay behind the car in front of me or turn off my brights because of oncoming traffic? Rules can come with good intentions, and they can also take over and strangle the life out of us and others.
It is at this point that Jesus turns to the question of attitude. Some Pharisees, like so many Christians, lost sight of the main point. It comes down to our hearts. Evil comes from the inside out, not from the outside in. What you eat can't really make you unclean in any meaningful sense. Uncleanness is a matter of a person's heart or intentions. Out of the heart come the evil things that truly defile us (Mark 7:21-23).
This is Ethics 101. Jesus here gives us the core fundamentals of what is important to God. Yes, the specifics of what we do can be important. If I kill someone, that is very significant, no matter why I did it. But God's evaluation of me is solely based on my intentions. Did I intentionally kill the person? Why did I do it? Was I trying to protect someone? Was I negligent?
Notice that what I know is the least important element in the moral equation. The implication would seem to be that my specific beliefs are the least important aspect of who I am as I stand before God. Paul also says that "everything that does not come from faith is sin" (Rom. 14:23). He is saying that far more important than what I believe is that I act with complete commitment to God in relation to whatever I believe.
Wrong beliefs can be harmful to myself and others, to be sure. It is important not to harm or wrong others--even with good intentions. But in the long run, my attitude is the first and most important order of business as far as morality is concerned.
This is the recurring critique of the Pharisees in the gospels.  They "strain out a gnat and swallow a camel." They may go to great lengths to keep a little gnat out of their cereal bowl while crunching on some rather large cockroaches. Jesus didn't criticize the Pharisees for being strict. He didn't have a problem with them tithing a tenth of various spices--a tenth of my mint to the temple, a tenth of my cummin, a tenth of my dill (Matt. 23:23). He didn't criticize them for straining out the gnats.
The problem was that they missed the really important aspects of the Law: justice, mercy, and faithfulness. In fact, the individuals in view here used the technicalities of the Law to get out of keeping these core values. While the purpose of taking an oath is to guarantee to someone else that you are telling the truth, some apparently swore by things they thought didn't count so that they could give the appearance of telling the truth while still lying. So they swore by the temple or altar instead of the gold in the temple or the sacrifice on the altar (Matt. 23:16-19).
Jesus calls this approach to morality hypocrisy, putting on a good show on the outside while having nothing of value on the inside...
 See chapter 3 for the important reminder that not all Pharisees were this way. For example, Nicodemus in John 3 is a Pharisee and some Pharisees became Christians and yet were able to remain Pharisees too (cf. Acts 15:5; 23:6).