Nativity as Renewal of Mankind

God, having formed man with His own hands in His own image He in his love allowed man free will to follow his own initiative.  Because of the deceit of the devil man was not strong enough to withstand his temptations and separated himself from God.  God then through the incarnation set about to recreate man anew.

Saint Gregory Palamas puts it this way,

So now God not only forms human nature anew by His own hand in a mysterious way, but also keeps it near Him.  Not only does He assume this nature and rase it up from the fall, but He inexpressibly clothes Himself in it an unites Himself inseparable with it and born as both God and man: from a woman, in the first instance, that He might take upon Himself the same nature which He formed in our forefathers; and from a woman who was a virgin, in the second, so that He might make man anew.

The Incarnation is an integral part of God's plan for mankind.  With free will so man could mature in His likeness to love God with his whole heart and mind just as God loved man, mankind was lost, separated from God and unable on His own power to reunite himself with God.  Through the Incarnation God renewed mankind.

Saint Gregory tells us,

If He had been born from seed, He would not have been a new man and, being part of the old stock, and inheriting that fall, He would not have been able to receive the fullness of the incorruptible Godhead in Himself and become an inexhaustible source of hallowing.  And so, not only would He not have been able to cleanse,  with abundance of power, our forefathers defilement caused by sin, but neither would He have been sufficient to sanctify those who came later....

God in His incarnation gave us more than a one time event.  His renewal of Mankind established an eternal spring of healing water by training the Apostles who with the power of the Holy Spirit established the Church as an unending source of His healing power for mankind to be renewed from ages to ages.

Saint Gregory says,

But creation needed a well containing it own spring, that those who drew near it and drank their full might remain undefeated by the attacks of weaknesses and deprivations inherent in the created world.... Building now the new Jerusalem, raising up a temple for Himself with living stones and gathering us into a holy and world wide Church, He sets in its foundation, which is Christ, the ever-flowing fount of grace.

Today we have this "ever-flowing fount of Grace in His presence in His Church.  The incarnation calls all of us to be partakers of this grace through our way of life.  Through our daily prayer, repentance, participation in the Sacraments we are filled with the Holy Spirit  to live the virtuous life He taught us in His life as fully man here on earth. We can think of the Nativity as much more than the birth of a chid in a manger.  It is also the birth of His Church though which we participate to this day to come in unity with Him learning to live the virtuous way of life he showed us to be possible once we were renewed by becoming part of Him in His Church.