From this lowliness, however, a great miracle was presented. Consequently, the mere sight of that Sacred Infancy to which God the Son of God had adapted himself was bringing to their eyes a preaching that would be imparted to their ears. What the sound of his voice was not yet presenting, the activity of sight was teaching them. For the entire victory of the Savior, the one that overcame the devil and the world, began in humility and ended in humility. Its appointed time began under persecution and ended under persecution. Neither the endurance of suffering was lacking to the child, nor the gentleness of a child to the one who would suffer. For, the Only-Begotten Son of God undertook by a single inclination of his majesty both the will to be born as a human being and the ability to be killed by human beings.
Almighty God, therefore, made our extremely bad situation good" through his unique lowliness and "destroyed death" along with the author "of death." He did not refuse anything that his persecutors brought down on him. In obedience to the Father, he bore the cruelties of violent men with the meekest docility. How humble we ought to be, then, how patient, we who, when we meet with any distress, never undergo anything we do not deserve! "Who will boast that they have a pure heart or that they are clean from sin?" (Prov. 20,9). Blessed John says, "If we say we have no sin, we are deceiving ourselves and the truth is not in us." (1Jn. 1, 8)
Who will be found so free from guilt that they have not in themselves anything for justice to condemn or mercy to forgive? Consequently, dearly beloved, the whole learning of Christian wisdom consists not in abundance of words, not in cleverness at disputing, not in desire for praise and glory, but in a true and willing humility. This is what the Lord Jesus Christ chose and taught from within the womb of his Mother right up to his torment on the cross - by enduring everything with fortitude. When the disciples, as the Evangelist says, arguing among themselves as to "which one of them would be greater in the kingdom of heaven, [Jesus] called a little child and stood him in their midst and said: 'Amen, I say to you, unless you change yourselves and become like little children, you will not enter the kingdom of heaven. Whoever, therefore, humble themselves like this child will be the greater in the kingdom of heaven."
Christ loves the Childhood that he first took up in both soul and body. Christ loves childhood, the teacher of humility, the rule of innocence, the image of gentleness. Christ loves childhood, to which he directs the characters of older people, to which he brings back old age. Those whom he would raise up to an eternal kingdom he disposes to follow his own example."
St. Leo the Great, Sermon 37, Epiphany, 2 – 3.
Source : (http://www.vatican.va/spirit/documents/spirit_20000804_leone-magno_en.html)