This will be brief. I will just list a passage that is often debated.
"Hear ye the word which the LORD speaketh unto you, O house of Israel: Thus saith the LORD, Learn not the way of the heathen, and be not dismayed at the signs of heaven; for the heathen are dismayed at them. For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe. They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not. They are upright as the palm tree, but speak not: they must needs be borne, because they cannot go. Be not afraid of them; for they cannot do evil, neither also is it in them to do good." Jeremiah 10:1-5
Whether our readers may protest that this may have anything to do with Christmas trees, the part of this passage that truly matters is this:
God just simply tells us not to follow after the rest of the world. The world observes this day, and that day and they have their own traditions. As Christians, we're to have no part with it. It is all vanity in the eyes of God. We're not of this world, and even that should be blatantly obvious to everyone else but unfortunately... you don't see that anymore.
Many Christians will argue and say that if we make this holiday about Christ, then it'll be okay to celebrate. If we think about it, does God want that? Does He want us to take something wicked, and then make it good, for His sake? Or does He ask us to be separate from the wicked thing altogether?
"Ye cannot drink the cup of the Lord, and the cup of devils: ye cannot be partakers of the Lord's table, and of the table of devils." 1 Cor 10:21
Many of us know that December 25th isn't Christ's birthday. He also never commanded us to celebrate His birthday, but to observe His death and its purpose. Could we just be trying to justify our decision in partaking with this holiday, by making it about Christ for our own selfish motives? I don't mean to sound harsh, but what other motive could it be, if it is not God's? We should evaluate ourselves.
Many will argue that God does not want to deprive us of joy. Well, God reminds us in the Bible that He doesn't want us to seek empty joy from the world, or joy from satisfying our own carnal desires. He wants us to find joy in HIM alone, and for that to be sufficient. True joy is only through Him.
Christmas is a day with the most dazzles, lights, glitter, and the most appealing things. Don't forget the nature of Lucifer. He draws us in and allures us by his brilliant appearance, and appears to us as an angel of light. It is in this day when we are brought to financial burdens, find ourselves in debt, and when we feed our fleshly desires the most. Wouldn't you agree that it is the opposite of what God seeks from us?
Behold the Lord, not the world. Come out and be separate.