Jesus had many followers. We read that, on another occasion, Christ selected seventy disciples and send them out on a missionary journey. Of the many disciples, twelve were selected and appointed as apostles (Mark 3:14). The authority of Jesus, which was exclusive to him up until this point (Mark 1:27, Mark 3:11), is now shared with the Twelve that was with him.1
Jesus promised them specific authority because they would become the new spiritual leadership (Luke 22:29–30). Later, Paul stated that the mark of a true apostle is this authority: with signs and wonders and mighty works
(2 Corinthians 12:12). The authority was not only for exorcism, but also for healing and preaching (Matthew 10:1; Luke 9:1–2). It was in this authority, bestowed on the apostles, that they would continue the work of Christ after his ascension. Christ also gave authority to some of his followers, other than the Twelve (Luke 10:1–12), that he sent on another mission, but it was limited to that mission only.
7 And he called the twelve and began to send them out two by two, and gave them authority over the unclean spirits.