“And he went up on the mountain, and called to him those whom he desired; and they came to him. And he appointed twelve, to be with him, and to be sent out to preach and have authority to cast out demons: Simon whom he surnamed Peter; James the son of Zebedee and John the brother of James, whom he surnamed Boanerges, that is, sons of thunder; Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and Simon the Cananaean, and Judas Iscariot, who betrayed him."- St. Mark 3:13-19
Christ’s earthly ministry clearly was a divine mission, reflecting the mind and intention of God, and yet there were many practical things to take into consideration. He had, by this time, clearly stated the purpose of his earthly ministry. He had gone throughout Galilee preaching and healing, and had begun to make a sizable impact upon people in that area.
Jesus knew that the time of His own earthly ministry was limited, and even though He was God Incarnate, He was still only able (because of his human nature) to reach a limited number of people. There were no newspapers, no television, certainly no internet! To solve these two problems (the time limitation, and the limited numbers he could reach) He chose certain men to be with Him, to learn from Him, to be formed by Him, and who would be given the specific task of carrying on His work after His death and resurrection.
In choosing these men, Jesus called them for two purposes. Firstly, he called them to be with Him. They were to be His companions. They were to be with Him from that time on. Other people might come and go, the crowds might be there one day, and be gone the next, others might fluctuate in their attachment to Him, but these twelve were to identify their lives with His life and live with Him all the time. Secondly, Jesus called them in order to send them out (this is what “apostle” means: “one who is sent”). They were to be His representatives. They were to tell others about Him and His gospel. Just as they had been called by Jesus, so they were to call others to Jesus.
And for all of this, Jesus equipped the apostles with two things. He gave them a message; that is, the Gospel. They were made the “heralds” of Christ, announcing the Good News which Jesus was making clear in His own preaching and teaching. And He gave them power. He told them that they would have authority to cast out demons, able to exercise power over the destructive power of evil. In other words, His power was to be their power.
These facts begin to outline for us not only the ministry of the apostles, but also that of their successors the bishops, and indeed, the whole Church.