The four Gospels reveal that Jesus amazed people during His earthly ministry in two main ways. First, the signs and wonders He performed were unlike anything they had ever seen (Mark 4:35–41; John 11:38–45). Second, people were awestruck by our Lord's teaching, both by the insight of His interpretation of the Old Testament (Matt. 22:23–33) and by His evident authority.
Mark tells us that people were astonished at the authority of Jesus when He taught at the synagogue in Capernaum (Mark 1:21–22). This important Galilean city was located on the main trade route between Damascus and the Mediterranean coastal plain, making it an ideal home base of sorts for our Lord's ministry. In Capernaum, Jesus could teach local Jews and those who were passing through on their way elsewhere. With respect to authority, the Jews paid heed to the teaching of the scribes, who occupied an important place in first-century Jewish society. Scribes were experts in the Old Testament law, and the people regarded their Scriptural interpretations as binding. Because of this, and because scribes took care of the scrolls on which the Bible was written, scribes held seats of honor in the synagogues. One had to be a scribe to sit on the Sanhedrin, the ruling body of Jews, and the scribes also served as civil lawyers. In any case, the scribes taught by citing the opinions of various rabbis on different matters, appealing not to their own authority but to the authority of others.
Christ, on the other hand, did not appeal to the authority of various rabbis when He instructed the people. Rather, as Matthew Henry comments, Jesus taught "as one that knew the mind of God, and was commissioned to declare it." Mark does not record as much of Jesus' instruction as the other gospels do, so let us consider passages such as Matthew 5:21–48 in order to get an idea of what it meant for Jesus to teach with authority. There, we read how Jesus contrasted His understanding of the old covenant Scriptures with the understanding of the scribes. He did not quote the teachings of the scribes and rabbis as binding, but He expected others to see His teaching as superseding theirs. In fact, He taught with the authority of God Himself. The Greek word exousia, translated "authority" in Mark 1:22, is typically used in the Bible for God's own authority. Jesus did not rely on the expertise of others. He spoke the very words of our Creator (see John 12:49–50).
Jesus is often regarded as a good teacher, but as many Christian apologists have noted, we insult Christ if we view Him as merely a good teacher. Our Lord was not simply a wise moral philosopher; rather, He spoke with divine authority. What He says, therefore, must be believed. His Words are truth itself, and if we do not heed what He says, then we will find ourselves outside of His kingdom on the last day.