Jesus doesn’t gain authority, rather He reveals His Authority. Jesus' authority is tied to his identity as Messiah, the anointed, the son of God (Mark 2). His authority is his essence, and He is demonstrating God's sovereign rule over all things. This has both spiritual (against darkness) and political (against the powers and kingdoms of this world) implications. Jesus doesn’t have to prove his authority, his words and actions and life are authoritative. Jesus doesn’t have authority because he does the things, rather He does the things because He’s God in flesh.