Mark 3:13–19
13 And he went up on the mountain and called to him those whom he desired, and they came to him. 14 And he appointed twelve (whom he also named apostles) so that they might be with him and he might send them out to preach 15 and have authority to cast out demons. 16 He appointed the twelve: Simon (to whom he gave the name Peter); 17 James the son of Zebedee and John the brother of James (to whom he gave the name Boanerges, that is, Sons of Thunder); 18 Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and Simon the Zealot, 19 and Judas Iscariot, who betrayed him.
Here Jesus chooses twelve of his followers to be his inner crew. Later he will choose an "inner-inner" crew of Peter, James and John. Each of these inner circles will be privy to certain teachings, responsibilities, and experiences that the rest of the crowd following Jesus will not. From this simple list there are a few important things we should see.
First, why did Jesus choose twelve? The number twelve recalls the twelve tribes of Israel, the twelve sons of Jacob (Genesis 35:22-26; 49:1-28). By choosing twelve Jesus is signifying a reconstitution of Israel! That is no small claim. This number is so significant that after Judas hangs himself after betraying Jesus, the remaining eleven disciples must appoint another follower of Jesus to be an apostle to round out the twelve (Acts 1:12-26). Their responsibilities don't only include the mission of this life, in Revelation 4 John's vision of heaven includes twenty-four thrones around the throne of God (see also Matthew 19:28). In my opinion, the most likely interpretation of this is the twelve sons of Jacob and the twelve apostles occupying those thrones. Again, by choosing twelve Jesus is indicating that the movement he is starting fulfills the old covenant with Moses and begins a new covenant under him.
Another thing to notice here is the names and order of the disciples listed. Peter is first in all of the lists of disciples in the gospels, signifying his leadership position among the disciples in the early church. Then he is followed by James and John; this constitutes the inner circle of disciples as noted earlier. Judas is also notably listed last in every list, with an indicator that he betrayed Jesus. That may seem cold but the fact that they list him at all proves their desire to tell the truth and not cover up anything, even the disgraceful things about their community.
It's also worth noting a few things about the disciples that we see in this list. First, none of them were religious leaders or people of notoriety or any clout to speak of. They were all relatively common folks, whom Jesus chose to start the greatest movement in history. Secondly, they likely had some interesting relational dynamics in the group. Jesus called James and John "Sons of Thunder", a name which implies "loud ones" or "hot-tempered pair". You can imagine how they got that name! Then you've got Matthew, a former tax collector. Jews didn't like tax collectors because they were supporters of the Roman occupation, as we've already noted. Zealots, like Simon, especially didn't like tax collectors. Zealots were a group of radical Jews who wanted to start a holy war to oust the Roman occupation. The meaning of Iscariot is uncertain, but it could imply that Judas was a part of a radical fringe group of Zealot assassins. With these group dynamics they undoubtedly had some heated discussion and lively moments together. But remember Jesus picked them! Maybe, as Jon has been talking about in church, some tensions are good. Maybe it's important for us to be in community with people we disagree with.