"You pay tithes of mint and dill and cummin, and have neglected the weightier things of the law: judgment and mercy and fidelity."To understand what the Lord was throwing out at them, you have to understand that everything growing from the earth was the subject of a tithe. Both in Leviticus and Deuteronomy, it's clear that one-tenth of every bit of produce from the ground was, technically, owed to the Levitical (priestly) class in exchange for the ministerial functions they performed at the Temple.
So what about mint, dill, and cummin? These were not grown in any great quantity; certainly nothing compared to wheat or barley or any other food crop. These were kitchen herbs, used not as a main food staple, but as something to spice up food. As such, it was grown in small quantities, and not really thought to be part of the tithe-able crops.
But not so with the Pharisees, who prided themselves (and made sure everyone knew about it) on the fact that they did tithe on the little bit of kitchen herbs they grew. This was their way of bragging that they kept the law to a meticulous (and some would say ridiculous) degree.
So what is Jesus saying to them? He's questioning how, on one hand, they could be so meticulous about the smallest details of observing the Law. But, on the other hand, they could also be so obstinate when it came to following the bigger precepts of the Law; things like judgment, mercy, and fidelity.
The other part of that passage is also great for the trivia value:
"Blind guides, who strain out the gnat and swallow the camel!"
A gnat is an insect, and as such, an unclean animal (not kosher). In fact, so is a camel (I mean unclean, not an insect). Pharisees would often strain their wine through a cheesecloth kind of gauze, to make sure they didn't accidentally consume an non-kosher animal. The "dig" Jesus is throwing at the Pharisees is that they went to great lengths to make sure they didn't eat a gnat, but had no problem gulping down a camel. It reminds me about the statement he makes about ignoring the plank in one's own eye while calling attention to the splinter in someone else's eye.
Jesus knew how to hit the Pharisees in a way that would hurt them. Uncleanliness. Not in the way of being dirty, but more about being unclean and thus unable to worship God properly. They prided themselves on a ritual purity that they believed set them apart from the common folk. The very name "Pharisee" is literally translated as "separated ones", meaning they stay holy by staying separate from the rest of the profane world.
"You cleanse the outside of cup and dish, but inside they are full of plunder and self-indulgence."
Pharisees believed that a cup or dish that was ceremonially unclean could not be used, but food that was obtained through theft or cheating was perfectly fine, as long as it was eaten in a ritually clean cup or dish.
What's it all about? Obsession with the externals. We try our best to make sure that we look, on the outside, to be good and upright. But how do we look on the inside? I remember part of a talk I heard once given at a youth group retreat, which spoke about the "3 views of me". The first view is how we see ourselves, which tends to be the most unflattering (since we're overly critical about ourselves). The second view is how others see us, and we spend a whole lot of time and effort making sure that others see us in a positive light. The third view is how God sees us; that's the one we need to spend our time working on to make perfect.