The answer to this question takes careful consideration, because the intention must be clear. As Bahá’ís believe that all religions come from God, they could, in principle, celebrate Christmas and the other holidays of the Christian faith and other religions. But would it be a good idea? We should consider two things:
First of all, Bahá’u’lláh, the Messenger of God for our age, brought us new teachings for a new Age. He gave us a new calendar with new Holy days. Good occasions for us to celebrate and give gifts are, for example, intercalary Days and Naw-Ruz.
Another thing to remember is this : if Bahá’ís would start to celebrate Christmas, other people who do not know that they are Bahá’ís could think that they were Christians. People would be even more confused if Bahá’ís would also start celebrating the Holy days of other religions. In order to avoid such confusion, the beloved Guardian counselled the friends to no longer celebrate days like Christmas and the New Year with other Bahá’ís.
But, as you know, not everybody is Bahá’í : many Bahá’ís come from Christian families who celebrate Christmas ! There is nothing wrong for Bahá’ís to celebrate Christmas with their families. Sometimes, Bahá’ís are invited to Christmas celebrations with their friends : all this is fine, because Bahá’u’lláh taught that Bahá’ís must maintain cordial relationships with the followers of all religions. You must remember, though, that Bahá’í families and Bahá’í communities do not celebrate Christmas with each other.
The Universal House of Justice hopes that this letter will help you a little to understand your mother’s advice.