Jesus deliberately formed the Twelve to be his appointed representatives. He called them first to be with him, and then sent them out to preach and to exercise his authority over demons.

Mark now turns from the pressure of the crowds to Jesus’ deliberate formation of a chosen group. Jesus goes up the mountain, a setting that gives this moment special weight, and he calls those he wants. Throughout the passage, the emphasis remains on Jesus’ initiative: he goes up, calls, appoints, and gives names. At the same time, the men truly respond, because Mark tells us that they came to him.

Jesus appoints, or formally constitutes, twelve men, and that number matters. It is not simply a practical team size. It likely points back to the twelve tribes of Israel and shows that Jesus is doing something foundational in relation to the people of God. Mark does not unfold all the implications here, but the number is clearly significant.

The passage also makes clear why Jesus appoints them. First, they are appointed to be with him. This is not a small detail before the real work begins; it belongs to the calling itself and forms the foundation of their later mission. Nearness to Jesus comes before public ministry. Second, they are appointed so that he may send them out to preach and to have authority to cast out demons. The title "apostles" means "sent ones," which fits this commissioned role. They go out as Jesus’ representatives, not on their own authority.

The authority they receive is delegated authority. It is not personal power, natural influence, or self-made status. Jesus gives them authority specifically over demons, which fits the surrounding context, where his power over unclean spirits has already been displayed and will remain a major theme. The best reading of verse 15 is the shorter one, which speaks of authority to cast out demons without adding "to heal diseases." That reading keeps Mark’s focus especially on Jesus’ conflict with demonic powers in this section.

Mark then lists the twelve by name. Jesus gives Simon the name Peter, and he gives James and John the name Boanerges, which Mark explains means "sons of thunder." These are not casual nicknames. They show Jesus’ authority to define the identity and place of those he appoints.

The list ends with Judas Iscariot, and Mark adds, "who betrayed him." Judas is not betraying Jesus at this moment, but Mark tells us this now so that the coming conflict already casts its shadow over the newly appointed group. The note also warns readers that privileged nearness to Jesus and access to ministry do not, by themselves, guarantee faithfulness.

So this passage is more than a report that Jesus gathered helpers. He formally formed the Twelve as a defined body of representatives. They are marked by being with him, then being sent by him, and being entrusted with ministry under his authority. The scene carries both promise and warning: promise in Jesus’ purposeful formation of his representatives, and warning in the presence of Judas within the circle.