A cup of water is far less than “following us.” Most important, however, is not what people give to the apostles, but why they give it. It does not have to be a sacrifice for all time (“following”). Such a sacrifice Jesus has asked for only in special cases (Mark 10:21). If only people recognize Jesus’ servants as his delegates, even if it is only by means of a cup of water to quench their thirst. Obviously the man who cast out demons in Jesus’ name did not show disrespect for the disciples. He even listened to them when they ordered him to stop casting out demons so long as he did not belong to the real followers. This recognition of his delegates, Jesus will reward.1
41 For truly, I say to you, whoever gives you a cup of water to drink because you belong to Christ will by no means lose his reward.