And they came to Caperna-um; and when he was in the house he asked them, What were you discussing on the way? But they were silent; for on the way they had discussed with one another who was the greatest. And he sat down and called the twelve; and he said to them, If any one would be first, he must be last of all and servant of all. And he took a child, and put him in the midst of them; and taking him in his arms, he said to them, Whoever receives one such child in my name receives me; and whoever receives me, receives not me but him who sent me.
John said to him, “Teacher, we saw a man casting out demons in your name, and we forbade him, because he was not following us.” But Jesus said, Do not forbid him; for no one who does a mighty work in my name will be able soon after to speak evil of me. For he that is not against us is for us. For truly, I say to you, whoever gives you a cup of water to drink because you bear the name of Christ, will by no means lose his reward.
Revised Standard Version*
*8:33 What were you discussing on the way? Lit. What … among yourselves were you arguing? [Τί … πρὸς ἑαυτοὺς διελογίζεσθε;]. Compare KJV: What was it that ye disputed among yourselves by the way? See also v.34.
8:38 Teacher, we saw a man casting out demons in your name. RSV and other versions omit who does not follow us after we saw a man.
9:41 whoever gives you a cup of water to drink because you bear the name of Christ. Greek text reads ὃς γὰρ ἂν ποτίσῃ ὑμᾶς ποτήριον ὕδατος ἐν τῷ ὀνόματί μου, ὅτι Χριστοῦ ἐστε: whoever will give you a cup of water to drink in my Name, because you belong to Christ (EOB:NT)
(Mark 9:33-37, Eastern Orthodox Bible New Testament).
The disciples still were so human in their thinking that they quarrelled with one another over which one of them was the greatest, and was most favored by Jesus. The Lord does not forbid us to desire to become His favorites, for He wants us to desire advancement in the spiritual life. But He does not want us to grasp for honors and privileges, but rather to acquire the heights by humility. The Lord set a little child in their midst, and He wants us also to be like that little child. For a little child neither longs for fame, nor envies, nor bears grudges. And the Lord says, “Not only will you receive a great reward if you yourselves become like little children, but even if you only give honor for My sake to others who have become like little children [i.e. give honor to the saints and glorify them in Christ’s name], you will receive the kingdom of heaven. You receive Me, and by receiving Me, you receive the One Who sent Me.” See then what great things are achieved by humility, and by a simple, straightforward, and guileless manner. For both the Son and the Father dwell within us, and, clearly, the Holy Spirit does so as well.
– Theophylact of Ochrid (11th c.), The Explanation of the Holy Gospel According to St. Mark (tr. Fr. Christopher Stade, St. John Chrysostom Press, 2006)
John, who was called the son of thunder, was not acting out of jealousy and spite when he forbade the man who was casting out demons, but John wanted all who called upon the name of Jesus to also follow Jesus, and he wanted all the Lord’s disciples to be one body. For at the beginning of the Lord’s preaching, there were some who were ruled by the love of vainglory and wanted to work miracles themselves. When they saw that the name of Jesus was powerful to do many things, they called upon this name, and indeed they worked miracles, although they were unworthy of divine grace. They were permitted to work miracles because the Lord wished to spread abroad His preaching, even by means of those who were unworthy. What then does the Saviour answer? He does not permit John to forbid the man who was working miracles in His name, but says, “Let him be; for there is no man who shall be able easily to speak ill of Me if he shall work a miracle in My name. For how could one speak ill of Me who uses My name as the source of his own fame, and works miracles by calling upon My name?” The Lord here might appear to contradict Himself. For in another place He says, “He who is not with Me is against Me” [Luke 11:23]; but now He says, “He that is not against us is for us.” These words seem contradictory, but they are not. For the first, “He who is not with Me is against Me,” was spoken concerning the demons who strive to draw away from God those who are with God, and to scatter them. But here Christ is speaking of men who, on the contrary, by working miracles are leading some to God.
– Theophylact of Ochrid
Not only, He says, do I not forbid such a one who is working miracles in My name, but even if he should give you the smallest thing for My name’s sake, and should receive you on account of Me and not just as a human or worldly favor, he shall not lose his reward. The Lord mentions a cup of water because of those who use their own poverty as an excuse. For He says, even if you give something as insignificant as a cup of water, you shall not lose your reward.
– Theophylact of Ochrid