Mithra was an ancient sun god from Persia who was adopted by the Roman nobility. Some aspects of Mithra’s worship were adopted by early Christians. Some examples of these beliefs include: Mithra’s birthday was December 25th and his sacred day was Sunday. https://www.ancient-origins.net/myths-legends/cult-mithra-sacred-temples-and-vedic-legends-and-ancient-armenian-understanding-006423