R.C. Sproul
R.C. Sproul makes this contribution to the discussion of Christmas.

“That question comes up every year at Christmastime. In the first place, there’s no direct biblical commandment to celebrate the birth of Jesus on December 25. There’s nothing in the Bible that would even indicate that Jesus was born on December 25. In fact, there’s much in the New Testament narratives that would indicate that it didn’t occur during that time of year. It just so happens that on the twenty-fifth of December in the Roman Empire there was a pagan holiday that was linked to mystery religions; the pagans celebrated their festival on December 25. The Christians didn’t want to participate in that, and so they said, “While everybody else is celebrating this pagan thing, we’re going to have our own celebration. We’re going to celebrate the thing that’s most important in our lives, the incarnation of God, the birth of Jesus Christ. So this is going to be a time of joyous festivities, of celebration and worship of our God and King.”

I can’t think of anything more pleasing to Christ than the church celebrating his birthday every year. Keep in mind that the whole principle of annual festival and celebration is deeply rooted in ancient Jewish tradition. In the Old Testament, for example, there were times when God emphatically commanded the people to remember certain events with annual celebrations. While the New Testament doesn’t require that we celebrate Christmas every year, I certainly see nothing wrong with the church’s entering into this joyous time of celebrating the Incarnation, which is the dividing point of all human history. Originally, it was intended to honor, not Mithras or any of the other mystery religion cults, but the birth of our King.

Incidentally, Easter can be traced to Ishtar in the ancient world. But the Christian church coming together to celebrate the resurrection of Jesus is hardly something I think would provoke the wrath of God. I wish we had more annual festivals. The Roman Catholic Church, for example, celebrates with great joy the Feast of the Ascension every year. Some Protestant bodies do, but most do not. I wish we would celebrate that great event in the life of Christ when he was raised up into heaven to be crowned King of kings and Lord of lords. We celebrate his birth; we celebrate his death. I wish we would also celebrate his coronation.

J.I. Packer
Here is J.I. Packer, in Knowing God, chapter 5

But in fact the real difficulty, the supreme mystery with which the gospel confronts us, does not lie here at all [he was discussing the atonement, resurrection, and Gospel miracles]. It lies not in the Good Friday message of atonement, nor in the Easter message of the resurrection, but in the Christmas message of Incarnation. The really staggering Christmas claim is that Jesus of Nazareth was God made man–that second person of the Godhead became the “second man” (1 Cor 15:47), determining human destiny, the second representative head of the race, and that he took humanity without loss of deity, so that Jesus of Nazareth was a truly and fully divine as he was human.

Here are two mysteries for the price of one–the plurality of persons within the unity of God, and the union of Godhead and manhood in the person of Jesus. It is here, in the thing that happened at the first Christmas, that the profoundest and most unfathomable depths of the Christian revelation lie. “The Word became flesh” (Jn 1:14); God became man; the divine Son became a Jew; the Almighty appeared on earth as a helpless human baby, unable to do more than lie and stare and wriggle and make noises, needing to be fed and changed and taught to talk like any other child. And there was no illusion or deception in this: the babyhood of the Son of God was a reality. The more you think about it, the more staggering it gets. Nothing in fiction is so fantastic as is this truth of the Incarnation (Knowing God, IVP, 1973, p53).

Later on in Knowing God Packer writes:

It is our shame and disgrace today that so many Christians–I will be more specific: so many of the soundest and most orthodox Christians–go through this world in the spirit of the priest and the Levite in our Lord’s parable, seeing human needs all around them, but (after a pious wish, and perhaps a prayer, that God might meet those needs) averting their eyes and passing by on the other side. That is not the Christmas spirit. Nor is it the spirit of those Christians–alas, they are many–whose ambition in life seems limited to building a nice middle-class Christian home, and making nice middle-class Christian friends, and bringing up their children in nice middle-class Christian ways, and who leave the submiddle-class sections of the community, Christian and non-Christian, to get on by themselves.

The Christmas spirit does not shine out in the Christian snob. For the Christmas spirit is the spirit of those who, like their Master, live their whole lives on the principle of making themselves poor–spending and being spent–to enrich their fellow humans, giving time, trouble, care and concern, to do good to others–and not just their own friends–in whatever way there seems need.

There are not as many who show this spirit as their should be. If God in mercy revives us, one of the things he will do will be to work more of this spirit in our hearts and lives. If we desire spiritual quickening for ourselves individually, one step we should take is to seek to cultivate this spirit. “You know the grace of our Lord Jesus Christ, than though he was rich, yet for our sakes he became poor, so that you through his poverty might become rich” (2 Cor 8:9). “Your attitude should be the same as that of Christ Jesus” (Phil 2:5). “I will run the way of thy commandments, when thou shalt enlarge my heart” (Ps 119:32 KJV).