Matt7:28 And when Jesus finished those sayings the crowds were astonished at his this teaching.
29. For he was teaching them as one who had authority, and not as the scribes.
As he began to expound on the word of God they were amazed at his teaching. Because he was preaching with such authority. The reason why they were so amazed was because he didn’t teach as the scribes taught. They probably thought where is he getting his authority from. Most of them probably were thinking he is the son of Mary and Joesph. But they didn’t realize he was getting his authority from God. The Father had given him the same authority to speak as he he done with us. If we speak with authority we can move mountains.