Christ-Mass, the solar rite celebrated at the solar solstice of winter, which relates to the rebirth of the solar light of the cosmic Christ within matter.
"Christmas is a cosmic event that must be performed in each one of us. The Nativity (Christmas) is absolutely individual. It is necessary for the Christ to be born in each one of us. The Nativity of the heart is urgent." - Samael Aun Weor, Tarot and Kabbalah
Learn more: Alchemical Symbolism of the Nativity of Christ