I never use religious sentiments on any sort of card because first and foremost I need to be be true to myself. For sympathy cards I put a sentiment I would like to hear. It may be just 'Thinking of you' or 'I'm so sorry for your loss'. Even a devoutly religious person would not be offended by that.
I gave up doing Christmas cards several years ago and now I send New Year cards to people I want to stay in contact with. New Year cards are easy: Happy New Year' is all you need!
To live a creative life, we must lose our fear of being wrong. Joseph Chilton Pearce