In the Sermon on the Mount, Jesus says,
‘Do not think that I have come to abolish the law or the prophets; I have come not to abolish but to fulfill. For truly I tell you, until heaven and earth pass away, not one letter, not one stroke of a letter, will pass from the law until all is accomplished. Therefore, whoever breaks one of the least of these commandments, and teaches others to do the same, will be called least in the kingdom of heaven; but whoever does them and teaches them will be called great in the kingdom of heaven.
Then, if you know the rest of the story, Jesus goes on to break all sorts of laws (healing on the Sabbath, claiming to be divine, turning tables over in the Temple, ignoring his mother’s requests, etc.). How can someone say they came to fulfill the law while simultaneously break it?
To obey the law means actions are directed by an outside or external things that forces compliance. For instance, if I do not pay my taxes the government will fine me. There is force that is outside or external to me that I am really responding to. If the external force was not present, then there is a likelihood that I would not obey the law. This is also why I all slow down when I drive by a police officer, but will speed up once I feel I am “at a safe distance.”
Fulfilling the law is different. Fulfilling the law comes by indirectly obeying the law.
Take the above examples, if I were to pay my taxes out of my internal delight, I am not paying them out of fear that I will be punished by some outside force. Rather, when I pay my taxes out of a personal choice, I am fulfilling the law, but not considering (thinking about the consequences) the law. If I were a person who loves to go the speed limit because I think don’t want to rush or if I think that driving slower is just more pleasurable, then I will not go over the speed limit. I am indirectly following the law.
Sometimes what looks like obeying the law, is really fulfillment of the law. And sometimes what looks like breaking the law is also fulfilling the law.
Jesus fulfilled the law, even as he breaks them.
For instance, not working on the Sabbath was a law. There was punishment if you did not obey the law. But this law was put into place in order to keep people from being abused and overworked. It was a law meant to protect people from being treated as objects. So when Jesus healed on the sabbath, yes he broke the law but in doing so the law was fulfilled. The law was intended to humanize people but was used to objectify people. As Jesus humanizes those he healed on the Sabbath, he broke the popular interpretation of the law, but fulfilled the law in full.
As you can see, It is much easier to obey than it is to fulfill the law. Because sometimes obeying the law means breaking it, and breaking the law often comes with consequences. The question Jesus poses to us is do we desire to fulfill the law or only obey it?