Seriously, this is not a difficult matter to resolve. However, we need to be careful about labeling things. Scripturally, there is no such thing as the "CHRISTIAN Sabbath." The Sabbath commandment was given to ancient Israel, not to Christians. The Christian Sabbath, the day on which Christians rest and worship is clearly SUNDAY! Christendom as a whole with a few exceptions such as Seventh Day Adventists have kept Sunday as their day of worship down through the centuries. So clearly, SUNDAY is the Christian Sabbath, if we insist on using that awkward terminology.
The Sabbath that Jesus Christ observed (AND BROKE), was not, however, Sunday or the first day of the week. We know for a fact, historically, the Sabbath being kept in the time of Christ's earthly ministry, was the SEVENTH day or Saturday. Actually from Friday sunset till Saturday sunset.
The calendar has been changed numerous times through the centuries, however, the seven day weekly cycle has NEVER been changed or tampered with. Even when they dropped TEN WHOLE DAYS out of the calendar to bring the calendar back in line with the Spring equinox, they did NOT change the weekly Sabbath. One day was say Tuesday November the 10th and the NEXT day became Wednesday November the 20th! The week stayed the same. As the Sabbath command was part of the Old Covenant Law, which Paul went to great length to inform us that we are no longer under, it makes little difference which day is the Sabbath of Israel. The Sabbath like ALL aspects of the law of Moses and the law of God, the Torah, the Old Testament, was a shadow of something to come. It pictured something to come that would be the spiritual fulfillment of this command. Jesus Christ was the fulfillment of the Passover lamb. Jesus was slain, and so it would be WRONG for us to continue to slay a Passover lamb every Passover season to cover our sins. Likewise, the Sabbath pictured entering into a REST with God from our own WORKS. Not just our weekly physical labor of earning a living, but ALL OF OUR OWN WORKS.
So, if one tries to KEEP the Sabbath after Christ as already fulfilled it (as with the Passover lamb), then by trying to keep the law you actually BREAK the law! Just like when Paul said if we are circumcised to fulfill the law of circumcision given to Abraham and Israel, to show out spirituality, we indeed "fall from grace." By works of law no flesh at all shall be justified Paul tells us. How can one REST FROM HIS WORKS by keeping (spiritual WORKS) the Sabbath LAW?
I am not sure if I am understanding what you believe the word says on Sabbath keeping...I do understand your opposition to Sunday being kept as though it is a Sabbath and I agree with that opposition. Do you feel that Saturday is supposed to be kept as Sabbath even by followers of Christ, or would you agree that Jesus IS our Sabbath. He IS our rest and therefore any literal day is of little significance? Like Paul who said that some keep a day as special others treat all days alike (paraphrased). We just have to believe the Scriptures: "Howbeit that was not first which is spiritual, but that which is natural; and afterward THAT WHICH IS SPIRITUAL" (I Cor. 15:46). After the physical comes the spiritual and then there is NO MORE PHYSICAL--it has all been replaced.
"While we look not at the things which are seen, but at the things which are not seen: for the things which are seen ARE TEMPORARY..." (II Cor. 4:18). I don't think I need to explain what "temporary" means.
Jesus didn't keep the Sabbath as a physical day of rest from Friday sunset till Saturday sunset and neither do I. As for the day of the Sun being a Christian day set aside for worship, is plain unscriptural poppycock. Jesus did not keep the physical weekly Sabbath according to the 4th commandment. But He certainly did KEEP THE SABBATH of His Father. To keep the Sabbath we must NOT do our own work. Jesus never did "HIS OWN WORK," and therefore Jesus kept the Sabbath of His Father EVERY DAY OF THE WEEK. When people ask me if I keep the Sabbath, I answer by saying: "Every day of the week." The Sabbath is a physical commandment that has a spiritual application just like all the physical commandments. Keeping the PHYSICAL just won't get the job done. You can "NOT commit adultery" all day long, and still end up in the lake of fire. That is only the physical part of the commandment which is only for babes and minors. Jesus gave us the real commandment: "DON'T EVEN LOOK on a woman to lust after her," or you have already broken the physical commandmnet to not commit adultery. The same is true for circumcision. ONLY circumcision of the heart is of any value to God. We are to live on a higher standard of morality than the TEN PHYSICAL commandments. What good does it do for one if he has not one physical image of a God, but has HUNDREDS OF SPIRITUAL IDOLS IN HIS HEART? In Matt. 12 Jesus and His disciples broke the physical letter of the law, but they KEPT THE SPIRITUAL INTENT of the law, hence, the traveled on the Sabbath, healed on the Sabbath, picked grain on the sabbath, and even told another man to "PICK UP AND CARRY" his bed, ALL OF WHICH WERE AGAINST THE SABBATH COMMANDMENT. Yet Christ like the Priest who ate the shew bread, WAS GUILTLESS.
I do NOT "spiritual away the Sabbath." Besides, if something is "spiritualized" it will not go away, seeing that the natural is temporary, but the spiritual is lasting (II Cor. 4:18).
Your statements proves that you do not understand the "spiritual rest" of the Sabbath day at all. The Sabbath pictures rest (actually and literally to "stop working"). What good is the physical sabbath for people who NEVER stop working. Not only do they do their "works of the law" during the week, but they actually do their "works of the law" on the Sabbath which pictures them STOPPING THEIR OWN WORKS! When you do you "work of the law" by KEEPING the physical Sabbath, you BREAK the spirit of the Sabbath which is to STOP YOUR WORKING AND LET GOD WORK IN YOU.Therefore, when people as me if I keep the Sabbath I always answer by saying, "YES, EVERY DAY OF THE WEEK." As long as you are doing YOUR work on the Sabbath, you will never "ENTER INTO GOD'S REST" (Heb. 4). Paul had many people who rejected the Gospel by being the same thing: "Ye observe days and months [month means MOON], and times, and years (Gal. 4:10). Paul could no more persuade them in his day to give up the physical and obey the spiritual (John 6:63), than I am able today.
If people can't DO SOMETHING PHYSICAL THEY DON'T FEEL SPIRITUAL. That's just the way it is. "Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the NEW MOON [as you are now trying to instruct me as necessary], or of the SABBATH DAYS [as you are also accusing me of 'spiritualizing away the Sabbath']" (Col. 2:16).You have failed to read and understand one of my recent Installments on "The Sermon on the Mount is for YOU." Yes, we are to "keep the commandments"--especially those codified as "The TEN Commandments." They are mentioned and repeated time and again in the New Testament, either in total or in parts. Now then, your reference: “Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.” (Gen.26:5), can hardly be summed up in the "seventh day of rest." Does the seventh day of rest constitute  God's voice,  God's charge,  God's commandments,  God's statutes, and  God's laws? And notice that "commandments, statutes, and laws" are all in the plural. Are ALL of those commandments, statues and laws only the one seventh day of rest? Yes, we are to keep God's commands and Jesus Christ's NEW commandments (living the law AS Jesus lived the law). But unfortunately, those who speak the loudest about keeping the seventh day sabbath are often those who have turned that commandment into an "Idol of the heart" wherein they worship and made a demigod out of their doctrines rather than what that commandments is supposed to teach. A couple of months ago I also gave a Bible Study on "Keeping Sabbath." It explains HOW we are to keep the sabbath. We are to keep it as Jesus kept it. Jesus mentioned time and time again how that He did not come to do His Own WORKS, but the WORKS of His Father.
Don't you understand that keeping the sabbath in spirit is to STOP DOING YOU WORKS, and letting the Spirit of God work IN YOU. That is how one "enters into His REST" (Heb. 4).
You also state that, "...the observance of the seventh day Sabbath is the identifying sign of a true Christian." Oh really? The orthodox Jews have keep the seventh day sabbath in the physical manner of sabbath keeping Christians, and they have done so for thousands of years. Are they "true Christians?" I think not. To totally reject Jesus as the Saviour. If one doesn't keep the Sabbath day in the spirit, all they will accomplish is a day off from work.
We are to be humbled, but I can honestly say that I have never met a "sabbath keeper" who was not puffed up over the fact that he keeps the "right" day. It is a badge of superiority over Sunday keeping Christians. If we can't get past the physical, the shadow, the type, we will never embrace THE REAL THING!
Many people as me if I keep the seventh day sabbath of rest? And I tell them all the same thing: Yes, of couurse, I keep it every day.
The physical weekly day of physical rest of the 4th commandment is for those who have not yet learned that what this day and commandment pictures is entering into the Rest of our Lord, which is something we keep every day of our life. One cannot both keep the physical day of rest and also be observing God's spiritual Rest, which covers every day of the week. Once God taught His people what Circumcision stood for a picture in the spirit, Paul taught to NOT be physically circumcised any longer. In fact, if one is physically circumcised as a work of salvation, HE FALLS FROM GRACE! (Gal. 5:1-4).
It is wrong to do our spiritual works ON ANY DAY OF THE WEEK. That is what the Sabbath is to teach us. We are NOT to do our works, but let God work IN US on every day of the week, not just the seventh. Keeping the physical weekly Sabbath is for those who have not yet come to obey the SPIRITUAL Sabbath of God's rest (Heb. 4:3-4).
The importance of this study is to show that a person can become a child of God only by the work of Jesus Christ on the cross. This new creation in Christ signifies to be rested in a spiritual day, which is Christ. Monday to Sunday are physical days that will cease to exist. But Christ, the spiritual day, is eternal. If Christ is a daily testimony in your life, you truly observe the Sabbath day.
8:1 There is therefore now no condemnation to them which are in Christ
Jesus, who walk not after the flesh, but after the Spirit.