What I have learned points to all sin destroying our otherwise perfect relationship with God. So all sin is so-called "mortal". Where? IIRC, Paul says in one of his letters to the Corinthians that to follow the laws of "Do not eat! Do not touch!" etc have the appearance of spirituality but really have little value in restraining human indulgence. While I think he meant this in regards to some persistent Jewish customs, I think this applies here as well. Are you talking about unmarried partners living (but not having sex) together? I wouldn't think it's necessarily a sin in itself - I have a Christian friend who lives with her boyfriend simply out of circumstance. They have separate bedrooms and everything. In what way do we not respect the Sabbath? The trip here is: are we observing the Sabbath to make sure we are in step with the old covenant law to the letter, or do we set aside a special day to honour God? Indeed he was a man, and yet he was also God as he proved repeatedly and ultimately when he rose from the dead. Ghost, about your claim that Christians have changed the Torah in making the Old Testament, I don't know where you're coming from with that. Regarding pre-marital sex... well, I've been doing a lot of searching on the 'net and the vast range of opinions really is quite interesting, if not confusing. Clearly, adultery - voluntary sexual activity with someone other than your spouse - is condemned. It could be seen that pre-marital sex is also condemned following on from that in that anyone you have sex with is also not your spouse. It might be true that pre-marital sex is not explicitly forbidden, but the commands that marriage and uniting of flesh (ie intercourse) go together is enough for me to remain happy to stay a virgin until when (or if) I am married. I think this is the 'safe' way to go, and it also carries some practical benefits in avoiding STIs, unwanted pregnancies, etc.