What is "morality"? What is "moral law"?
Morality is doing what you
ought to do.
Moral law is the law that governs moral agents. It is the obligations they have. It is "what people ought to do."
If people ought to keep the Sabbath, it is moral law. Period. It's oughtness is what makes it moral.
Morality or moral character is the condition of the person in regard to their fulfilling or failing to fulfill their duty, what they ought to do. It is immoral to disobey God because obedience to God consists in doing what God wants us to do. What God wants us to do is called "moral law", a code of conduct.
Saying that the Sabbath contains no spiritual benefit is in my opinion an indication of a very low regard for something God blessed, hallowed, sanctified, and gave to man as a gift.
God wants to His people call the Sabbath a delight, and offers a promise:
Isaiah 58:13-14 KJV
If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord , honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words: [14] Then shalt thou delight thyself in the Lord ; and I will cause thee to ride upon the high places of the earth, and feed thee with the heritage of Jacob thy father: for the mouth of the Lord hath spoken it .
If a person doesn't have that attitude towards the things of God, well, I guess they just don't. I don't understand why a Christian wouldn't think of the Sabbath as a delight, and honourable, that is, a REALLY GOOD THING.
Threaded Mode
