What is the message of Christmas?
J.I. Packer writes,
The Christmas message is that there is hope for a ruined humanity – hope of pardon, hope of peace with God, hope of glory – because at the Father’s will Jesus Christ became poor and was born in a stable so that thirty years later he might hang on a cross. It is the most wonderful message that the world has ever heard, or will hear. (Knowing God, p.63)
You cannot truly understand the manger apart from the Cross. And so you cannot truly understand Christmas apart from the gospel.
For you know the grace of our Lord Jesus Christ, that though he was rich, yet for your sake he became poor, so that you by his poverty might become rich. (2 Corinthians 8:9 ESV)