What matters the most for Jesus about or in the law in the Bible?
Jesus saw his life as a fulfilment of the law as written in the Old Testament, and the writers of the various gospels in the New Testament clearly link what happens and the events of Jesus's life to various verses in the Old Testament, particularly focused around the prophetical books, such as Isaiah, to indicate this. It is therefore perhaps evident that Jesus does not have a part of the law that is more important to him than others. Rather, for him, every part is just as significant as the rest, and he saw his life as being the natural culmination of so much of what was written in the ancient Jewish Old Testament. Note, for example, how this occurs at the beginning of the Gospel of Mark, when verses from the Book of Malachi are quoted to predict how John the Baptist was prophesied to announce the imminent arrival of Jesus, the Messiah:
I will send my messenger ahead of you,
who will prepare your way—
a voice of one calling in the wilderness,
‘Prepare the way for the Lord,
make straight paths for him.’
This is clearly linked in the beginning of Mark's Gospel to John the Baptist's function of "preparing the way" for Jesus. Throughout the Gospels, therefore, the Old Testament is referred to repeatedly in order to highlight the way in which Jesus fulfilled the law. It is better therefore to argue that Jesus did not have a part of the law that was more important than others, but saw his whole life as a fulfilment of that law.