While we don't have a specific commandment to celebrate Christmas, we do have Scriptural justification to celebrate Christ's birth.
Shortly after an angel of the Lord appeared to the shepherds on the night of Christ's birth, the Bible says "a multitude of the heavenly host" angels, were "praising God, saying, 'Glory to God in the highest, and on earth peace among men with whom He is pleased'" (Luke 2:13-14).
The angels of God celebrated the birth of Jesus. So, if we celebrate Jesus's birth with singing (e.g., Joy to the World, Silent Night, Away in a Manger), we are following the pattern laid out for us by the angels.
The critics of Christmas are right in saying God didn't instruct us to celebrate Christmas ("Celebrate my Son's birth once a year!"). But that may be why our celebrating Christ's birth might bless Him all the more. We are celebrating His gift out of love for Him, not because we have a command to obey, but because we freely want to celebrate and thank Him for His gift.
When my kids celebrate my birthday by making me a card, giving me a gift, or telling me something kind, I don't frown and say, "Stop it! I never commanded you to celebrate. Return the presents! Stop the kind comments!" No. I rejoice all the more that they would freely decide to celebrate and rejoice all on their own.
As followers of Jesus Christ celebrate Jesus's birth this Christmas with singing, with thankfulness, with generosity, kindness, giving gifts, etc. I am confident that God is delighted with the celebration. The angel told the shepherds, "Do not be afraid, for behold I bring you good news of a great joy [sounds like reason to celebrate] which shall be for all the people [sounds like you and me!]; for today in the city of David there has been born for you a Savior, who is Christ the Lord" (Luke 2:10-11).
A Savior being born to rescue humanity from our sin!? What a reason to celebrate! I pray you have a very blessed, Christ-focused Christmas celebrating with the angels "His indescribable gift!" (2 Corinthians 9:15).