Praise be to Allaah.
It is not permissible for a Muslim to eat things that the Jews and Christians make on
their festivals, or what they give him as a gift on their festivals, because
that is cooperating with them and joining in with them in this evil, as is
explained in question no. 12666.
It is not
permissible for him to congratulate them on their festivals in any way
whatsoever, because that implies approval of their festival and not
denouncing them, and helping them to manifest their symbols and propagate
their innovation, and sharing their happiness during their festivals, which
are innovated festivals that are connected to false beliefs that are not approved of in Islam. See also question no.
And Allaah knows best.