And it came to pass, when Jesus had ended these sayings, the people were astonished at his doctrine: For he taught them as one having authority, and not as the scribes.
In Israel, it was customary to teach by citing the source of your information- usually the rabbi you followed. For example, a scribe would preface his teaching by “I say unto you in the name of (insert name of teacher/rabbi) that ... (fill in the teaching). This gave the listener a chance to evaluate the teaching based on the prominence of the teacher’s name. When Paul wanted to stress the quality of his religious education, he informed his listeners that he had sat "at the feet of Gamaliel.” If you quoted a prominent Rabbi, then your words were given more weight by the listeners.
Samuel Lachs further explains, “The crowds were used to the type of preaching which characterized the Scribes-Pharisees. Their procedure was to teach the Oral Law by citing the authorities from whom the speaker received the traditions being transmitted. Failure to do so was considered not only a display of arrogance but destructive of the system, breaking the continuum of the process. This is emphasized in the statement "Anyone who says a thing in the name of one who said it brings deliverance to the world, as it is said, And Esther told it in the name of Mordecai [Esther 2.22]."
Jesus' presentation appeared strange to the people, who were accustomed to hearing citations together with the tradition taught. Jesus appealed to no such authority in his teaching, neither by name nor by inference. ... We may assume that originally “authority” had the meaning of “Rabbinic Authority.” The people were surprised that Jesus should teach like one ordained.”
(Lachs, Samuel Tobias. 1987. A Rabbinic Commentary on the New Testament. Hoboken, NJ: Ktav Publishing House, Inc., pgs 60-61)