It is important to understand what perspective the Jews had that they heard Jesus' teachings as such a revelation ... and not like the scribes. First we must look at how they viewed the Torah (the Law).
To the Jews the most sacred thing in the world was the Torah, the Law. The core of the law is the Ten Commandments, but the Law was taken to mean the first five books of the Old Testament, the Pentateuch, as they are called. To the Jews this Law was completely divine. It had, so they believed been given direct by God to Moses. It was absolutely holy and absolutely binding. They said, "He who says that the Torah is not from God has not part in the future world." "He who says that Moses wrote even one verse of his own knowledge is a denier and despiser of the word of God."All excerpts in this post are from: The Gospel of Mark (The Daily Bible Series, rev. ed.) by William Barclay
If the Torah is so divine two things emerge. First, it must be the supreme rule of faith and life; and second, it must contain everything necessary to guide and to direct life. If that be so the Torah demands two things. First, it must obviously be given the most careful and meticulous study. Second, the Torah is expressed in great, wide principles; but, if it contains direction and guidance for all life, what is in it implicitly must be brought out. The great laws must become rules and regulations -- so their argument ran.
* Not a Catholic source and one which can have a wonky theology at times, but Barclay was renowned for his authority on life in ancient times and that information is sound.