“For this reason he had to be made like his brothers in every way, in order that he might become a merciful and faithful high priest in service to God, and that he might make atonement for the sins of the people.” Hebrews 2:17
Christmas celebrates the birth of Jesus Christ. It was the physical incarnation of the son of God. By choosing to become a man, Christ gave up life in heaven, where he was lord over all and untouched by the corruption of sin. He traded that for the utter helplesness of a baby and was raised by a couple who had almost nothing. He lived a life that was destined to end on a cross at a lonely hill with two criminals. Sounds like the worst trade-off ever.
But the remarkable thing is that he considered it a gain. He did it becuase he wanted to spend eternity with us. He was willing to identify himself with Man in his fallen nature so that we could identify with Jesus in his holy nature. Everything that belongs to Christ is now ours, if we believe in him. The earth is ours, authority over angels and demons is ours, and a relationship with the Father is ours. All because of Christmas.