Summary: This passage does seem like two different smaller passages, but perhaps they are linked in that they both deal with how interact with other people's faith. In a day of partisan and even tribal politics if not religion, this passage can serve a powerful reminder of the need to be generous to other people's faith. If someone else is serving other people; if someone else is following Jesus, then they are on our team!
τινα ("someone", 9:38) The translations generally say "someone" or "a man" was trying to cast out demons. However, the Greek is a bit more vague. It simply is "tina" which can mean, someone, something, any, certain, a -- generally an indefinite marker. In otherwords, the disciples have dehumanized their opponents! The disciples did not stop to get the person's name or know his story!
εκωλυομεν (imperfect form of κωλυω, meaning "prevent", 9:38; 9:39) The tense of this verb is imperfect, indicating on-going action: "we continued to stop" or "we kept preventing." (The verb ηκολουθει "follow" is also in the imperfect tense). The disciples are really putting effort into stopping this man.
[[Greek grammar: One thing worth noting is that the participle for cast out is in the present tense. In translation though, its tense is governed by the finite verb, in this case "we saw" which is in the aorist. So the action of the casting out is present relative to the action of seeing.]]
μη κωλυετε ("no longer hinder", 9:39) Another lesson on Greek imperatives; the "μη" + present imperative construction suggests that the person was doing this action already (as in "do not be afraid" implies that the person was already afraid]. To translate then, "No longer hinder..."
υμιν ("us", 9:38) The pronoun is worth noting here: "υμιν" -- "not following us"! It is not about following Jesus, but about following the disciples. This can be a big trap for churches and denominations, worrying more about following us than about following Jesus! We are called not to hinder the faith of others and there are times when other people can believe things that are false or incredibly unhelpful. However, we must always ask ourselves -- not whether they have the doctrine all right -- but if they are following Jesus.
κακαλογεω ("renounced", 9:39) The word for "speak against" is a great one: κακαλογεω, from κακα (bad) and λεγω (speak). The word is more akin to blaspheme/renounce than simply slander. I wonder how much time we spend as Christians κακαλογεω-ing each other!
εχετε εν εαυτοις αλα, και ειρηνευετε εν αλλήλοις (9:50): Have salt in yourself and have peace among yourselves. There is a bit of a parallel structure here: εν εαυτοις and εν αλλήλοις; in yourself; in each other. The second time the word εν is used it almost has to be translated as "among." This doesn't change the meaning, I just wanted to show you how pithy Jesus made this ;-) But here is the deal, salt by itself is fairly useless, in fact, it is caustic. When it is used in proper doses with other things, it can be incredibly useful and flavorful. Don't be a big salt block by yourself :-) Share the love!
Some other little tid bits that one day I may work into a more coherent post:
9:43 The word for life (Zooeh = zwh) has an article before it: "The life." Interestingly Jesus here equates "the life" with "the kingdom of God."
9:39 Here we have a little play on words. The word for "deed of power/wonder" is "dynamis." The word for "able" is "dynamai" -- same root. If you do power in Jesus name, you do not have the power to speak evily of him.
9:41 The Greek text as "give a cup of water in name." What is missing? Jesus! It should read "name of Jesus" or "name of mine," which a good number of manuscripts have, including the classic case where editors were scribbling out each other's work. I think it is implied though!
9:41 Here we have the word from early in the call to discipleship: "Lose your life" (apollu-mi).
9:42 Both 9:41 and 9:42 describe to conditional events, namely, what happens to non-believers (or believers) based on their interaction with believers. Both cases are the "hos an" + subjunctive construction.
9:47 There are some fun words in here in these verses (skandaliz-oo; apokopt-oo) worth noting in this one is that Jesus returns to the exorcism and tells them that they should "cast out" (exball-oo) their own eyes...