Ambrose of Milan
Catena Aurea · Lukasevangelium 18
And they brought unto him also infants, that he would touch them: but when his disciples saw it, they rebuked them. But Jesus called them unto him, and said, Suffer little children to come unto me, and forbid them not: for of such is the kingdom of God. Verily I say unto you, Whosoever shall not receive the kingdom of God as a little child shall in no wise enter therein. They knew indeed the mystery, that to both nations the call was to be made, (for they entreated for the Canaanitish woman,) but perhaps they were still ignorant of the order. It follows, But Jesus called them unto him, and said, Suffer little children, &c. One age is not preferred to another, else it were hurtful to grow up. But why does He say that children are fitter for the kingdom of heaven? It is because they are ignorant of guile, are incapable of theft, dare not return a blow, are unconscious of lust, have no desire for wealth, honours, or ambition. But to be ignorant of these things is not virtue, we must also despise them. For virtue consists not in our inability to sin, but in our unwillingness. Childhood then is not meant here, but that goodness which rivals the simplicity of childhood.
Lastly, our Saviour expressed this when He said, Verily I say unto you, Whosoever will not receive the kingdom of God as a little child, &c. What child were Christ’s Apostles to imitate but Him of whom Esaias speaks, Unto us a Child is given? (Isai. 9:6.) Who when He was reviled, reviled not again. (1 Pet. 2.) So that there is in childhood a certain venerable antiquity, and in old age a childlike innocence.