Matthew 18:3

One whose tender age should express to them the innocence which they should have. But truly He set Himself in the midst of them, a little one who had come not to be ministered unto, but to minister; (Mat. 20:28.) that He might be a pattern of holiness. Others interpret the little one of the Holy Spirit, whom He set in the hearts of His disciples, to change their pride into humility. (Vid. Origen. in loc.) And he said. Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven. He does not enjoin on the Apostles the age, but the innocence of infants, which they have by virtue of their years, but to which these might attain by striving; that they should be children in malice, not in understanding. As though He had said, As this child, whom I set before you as a pattern, is not obstinate in anger, when injured does not bear it in mind, has no emotion at the sight of a fair woman, does not think one thing while he speaks another; so ye, unless ye have the like innocence and purity of mind, shall not be able to enter into the kingdom of heaven.

(interlin.) Except ye be converted from this ambition and jealousy in which you are at present, and become all of you as innocent and humble in disposition as you are weak, in your years, ye shall not enter into the kingdom of heaven; and since there is none other road to enter in, whoso shall humble himself as this little child, the same is greatest in the kingdom of heaven; for by how much a man is humble now, by so much shall he be exalted in the kingdom of heaven.

What then saith Christ? He unveils their conscience, and replies to their feeling, not merely to their words. "For He called a little child unto Him," saith the Scripture, "and said, Except ye be converted, and become as this little child, ye shall not enter into the kingdom of heaven." "Why, you," He saith, "inquire who is greatest, and are contentious for first honors; but I pronounce him, that is not become lowest of all, unworthy so much as to enter in thither." And full well doth He both allege that pattern, and not allege it only, but also set the child in the midst, by the very sight abashing them, and persuading them to be in like manner lowly and artless. Since both from envy the little child is pure, and from vainglory, and from longing for the first place; and he is possessed of the greatest of virtues, simplicity, and whatever is artless and lowly. Not courage then only is wanted, nor wisdom, but this virtue also, humility I mean, and simplicity. Yea, and the things that belong to our salvation halt even in the chiefest point, if these be not with us. The little child, whether it be insulted and beaten, or honored and glorified, neither by the one is it moved to impatience or envy, nor by the other lifted up. Seest thou how again He calls us on to all natural excellencies, indicating that of free choice it is possible to attain them, and so silences the wicked frenzy of the Manichaeans? For if nature be an evil thing, wherefore doth He draw from hence His patterns of severe goodness? And the child which He set in the midst suppose to have been a very young child indeed, free from all these passions. For such a little child is free from pride and the mad desire of glory, and envy, and contentiousness, and all such passions, and having many virtues, simplicity, humility, unworldliness, prides itself upon none of them; which is a twofold severity of goodness; to have these things, and not to be puffed up about them.