Origen's John

In that day came the disciples unto Jesus, saying, Who then is the greatest in the kingdom of heaven?” And, perhaps, they were also in doubt because of the preference which had been given to the three at the transfiguration, and they were in doubt about this-which of the three was judged by the Lord to be greatest. For John reclined on His breast through love, and we may conclude that before the Supper they had seen many tokens of special honour given by Jesus to John; but … because of the saying, "Get thee behind Me, Satan; thou art a stumbling-block unto Me, for thou mindest not the things of God hut the things of men," they were distracted in mind as to whether it was not he [Peter] but one of the sons of Zebedee, that was the greatest … So the disciples, therefore, came to Jesus and sought to learn, who was the greatest in the kingdom of heaven; and perhaps they wished to learn, hearing from Him sometimes like this, "A certain one is greatest in the kingdom of heaven; "… Let us seek to understand, from what is written, to the best of our ability, who this is. "For Jesus called a little child," etc.

… if any one who is a man mortifies the lusts of manhood … to such a degree that he has the condition of the little child who has not tasted sensual pleasures, and has had no conception of the impulses of manhood, then such an one is converted, and has become as the little children … [he can be] compared with those who are in training and have not advanced to so great a height of self-control, is he the greatest in the kingdom of heaven.

… [And] the little child which Jesus took to Him; since especially in such the Christ is, and therefore He says, "Whosoever shall receive one such little child in My name receiveth Me.” … Every one that gives his adherence to Jesus … according to the true history concerning Him, and by deeds done according to the Gospel … is on the way towards becoming as the little children; and it is impossible for him not to enter into the kingdom of heaven … [A]nother interpretation different from what is called the simpler may be uttered; whether as dogma, or for the sake of exercise, so to speak, let us also inquire what was the little child who was called by Jesus and set in the midst of the disciples. Now consider if you can say that the little child, whom Jesus called, was the Holy Spirit who humbled Himself [emphasis mine], when He was called by the Saviour, and set in the midst of the reason of the disciples of Jesus; if, indeed, He wishes us, being turned away from everything else, to be turned towards the examples suggested by the Holy Spirit, so that we may so become as the little children, who are themselves also turned and likened to the Holy Spirit … which Holy Spirit was called by Jesus, and, descending from His own perfection to men as a little child, was set by Jesus in the midst of the disciples. It is necessary, then, for him who has turned away from the desires of this world to humble himself not simply as the little child, but, according to what is written, "as this little child."
But to humble oneself as that little child is to imitate the Holy Spirit [emphasis mine], who humbled Himself for the salvation of men. Now, that the Saviour and the Holy Spirit were sent by the Father for the salvation of men has been declared in Isaiah, in the person of the Saviour, saying, "And now the Lord hath sent me and His Spirit.” You must know, however, that this expression is ambiguous; for either God sent, but also the Holy Spirit sent, the Saviour; or, as we have taken it, the Father sent both-the Saviour and the Holy Spirit. He, therefore, who has humbled himself more than all those who have humbled themselves in imitation of that little child, is the greatest in the kingdom of heaven. For there are many who are willing to humble themselves as that little child; but the man, who in every respect has become like to the little child who humbled himself, in the name of Jesus-especially in Jesus Himself,-in reality, would be found to be he who is named greater than all in the kingdom of heaven.

… But let us consider also the like account in the other Evangelists. Mark, then, says, that the Twelve reasoned in the way as to which of them was the greatest … According to Luke, however, the reasoning did not arise spontaneously in the disciples, but was suggested to them by the question, "which of them should be greatest." And Jesus, seeing the reasoning of their heart, as He had eyes that see the reasonings of hearts,-seeing the reasoning of their heart,-without being questioned, according to Luke, "took the little child and set him," not in the midst alone, as Matthew and Mark have said, but now, also, "by His side," and said to the disciples, not only, "Whosoever shall receive one such little child," or, "Whosoever shall receive one of such little ones in My name receiveth Me," but, now going even a step higher, "Whosoever shall receive this little child in My name receiveth Me." It is necessary, therefore, according to Luke, to receive in the name of Jesus that very little child which Jesus took and placed by His side. And I know not if there be any one who can interpret figuratively the word, "Whosoever shall receive this little child in My name." For it is necessary that each of us should receive in the name of Jesus that little child which Jesus then took and set by His side; for he lives as immortal, and we must receive him from Jesus Himself in the name of Jesus; and without being separated from him, Jesus is with him who receives the little child, so that according to this it is said, "Whosoever shall receive this little child in My name receiveth Me." Then, since the Father is inseparable from the Son, He is with him who receives the Son. Wherefore it is said, "And whosoever shall receive Me receives Him that sent Me." But he who has received the little child, and the Saviour, and Him that sent Him, is least of all the disciples of Jesus, making himself little. But, so far as he belittles himself, to that extent does he become great; as that very thing, which caused him the more to make himself little, contributes to his advance in greatness; for attend to what is said, "He that is least among you all the same is great; "but in other manuscripts we read, "The same shall be great."

…. But another might say that the perfect man is here called little, applying the word, "For he that is least among you all, the same is great," and will affirm that he who humbles himself and becomes a child in the midst of all that believe, though he be an apostle or a bishop, and becomes such "as when a nurse cherisheth her own children," is the little one pointed out by Jesus, and that the angel of such an one is worthy to behold the face of God. For to say that the little are here called perfect, according to the passage, "He that is least among you all, the same is great." and as Paul said, "Unto me who am less than the least of all saints was this grace given," will seem to be in harmony with the saying, "Whoso shall cause one of these little ones to stumble," and "So it is not the will of My Father in heaven, that one of these little ones should perish." For he, as has been stated, who is now little, could not be made to stumble nor perish, for "great peace have they who love the law of God, and there is no stumbling-block to them; " and he could not perish, who is least of all among all the disciples of Christ, and on this account becomes great; and, since he could not perish, he could say, "Who shall separate us from the love”…. wherefore it is said, "Whoso shall cause to stumble one of these little ones, and, "It is not the will of My Father which is in heaven that one of these little ones should perish." [Commentary on Matthew 13]