"Against you is for you" (kaq mwn uper mwn). Mark 9:40 has "against us is for us" (hmwn ... hmwn). The Koin Greek h and were often pronounced alike and it was easy to interchange them. So many MSS. here read just as in Mark. The point is precisely the same as it is a proverbial saying. See a similar saying in Luke 11:23 : "He that is not with me is against me." The prohibition here as in Mark 9:39 is general: "Stop hindering him" (mh kwluete, mh and the present imperative, not mh and the aorist subjunctive). The lesson of toleration in methods of work for Christ is needed today.