Based on this post by Joseph Scheumann:-
1. The incarnation was not the divine Son’s beginning.
Our Lord did not begin to exist with the virginal conception or with his birth in Bethlehem. No: the incarnation means that he who had no beginning began to be what he eternally was not – a human being.
2. The incarnation shows Jesus’ humility.
No ordinary king, Jesus did not come to be served, but to serve (Mk 10:45). His glorious humility (see Phil 2:6-8) was on display from Bethlehem to Golgotha.
3. The incarnation fulfills God’s ancient promises.
It was not random or accidental. It was in accordance with God’s eternal plan, and in fulfilment of prophecy (see, for example, Isa 9:6).
4. The incarnation is mysterious.
Some things remain secret, while others are to be known, believed, and celebrated (see Deut 29:29). The incarnation entails some impenetrable mysteries, but we confess with the Council of Chalcedon (451 A.D.) that Jesus is “recognized in two natures [God and man], without confusion, without change, without division, without separation; the distinction of natures being in no way annulled by union, but rather the characteristics of each nature being preserved and coming together to form one person and subsistence, not as parted or separated into two persons but one and the same Son and Only-begotten God the Word, Lord Jesus Christ.”
5. The incarnation is necessary for salvation.
Only God made flesh can provide a sacrifice that is effective in reconciling God and humanity. See, for example, Heb 2:17.
‘Our God is the eternal God who was born in a stable, not a distant, withdrawn God; our God is a humble, giving God, not a selfish, grabbing God; our God is a purposeful, planning God, not a random, reactionary God; our God is a God who is far above us and whose ways are not our ways, not a God we can put in a box and control; and our God is a God who redeems us by his blood, not a God who leaves us in our sin.’
Such is God’s greatness, as revealed in the incarnation of his Son!