I think a better question might be, "What did God mean by "keep the Sabbath day"?" We know that the Pharisees had this all worked out concerning what you could and couldn't do on The Sabbath. I'm not interested in what they thought
God meant. We can look all through the Gospels and see that they tried to trap Jesus over and over with this question. You could carry something in your pocket as long as you didn't go outside because if you carried something in your pocket outside it was considered work. Please! That ain't nothin' but some old man bored to distraction, with nothing else to do but meddle in people's lives!
Exo 20:8 Remember
the sabbath day
, to keep it holy
A primitive root; properly to mark (so as to be recognized), that is, to remember; by implication to mention; also (as denominative from H2145) to be male: - X burn [incense], X earnestly, be male, (make) mention (of), be mindful, recount, record (-er), remember, make to be remembered, bring (call, come, keep, put) to (in) remembrance, X still, think on, X well.H7676
Intensive from H7673; intermission, that is, (specifically) the Sabbath: - (+ every) sabbath.H3117
From an unused root meaning to be hot; a day (as the warm hours), whether literally (from sunrise to sunset, or from one sunset to the next), or figuratively (a space of time defined by an associated term), (often used adverbially): - age, + always, + chronicles, continually (-ance), daily, ([birth-], each, to) day, (now a, two) days (agone), + elder, X end, + evening, + (for) ever (-lasting, -more), X full, life, as (so) long as (. . . live), (even) now, + old, + outlived, + perpetually, presently, + remaineth, X required, season, X since, space, then, (process of) time, + as at other times, + in trouble, weather, (as) when, (a, the, within a) while (that), X whole (+ age), (full) year (-ly), + younger.H6942
A primitive root; to be (causatively make, pronounce or observe as) clean (ceremonially or morally): - appoint, bid, consecrate, dedicate, defile, hallow, (be, keep) holy (-er, place), keep, prepare, proclaim, purify, sanctify (-ied one, self), X wholly.
I've never looked this far into this but what I'm thinking now is this:
Exo 23:16 And the feast of harvest, the firstfruits of thy labours
, which thou hast sown in the field: and the feast of ingathering, which is in the end of the year, when thou hast gathered in thy labours out of the field.
Rom 11:16 For if the firstfruit be holy, the lump is also holy
: and if the root be holy, so are the branches.
In the New Testament Jesus tells us that he didn't come to destroy The Law but to fulfill it. (Matt. 5:17-48) Then he told us that unless our righteousness goes above that of the Pharisees, we won't make heaven. That tells me to look to The Word (Jesus), instead of The Law (men, especially those who expound on the law). In the Old Testament people brought the firstfruits of their labors: their harvests, their flocks, their businesses, etc. In the New Testament, the principle is the same: the firstfruits are holy. But, just as circumcision of the flesh was commanded in The O.T. Paul stated the heart should be circumcised in the N.T., so, I believe, when speaking of the Sabbath, we should look inward to the heart instead of outward, physical actions today.
Do I think a person should work on Sunday? That depends on what you're working at, not to sound like a Pharisee. I do not think you should engage in whatever it is you do for a living. You have 6 more days for that. Do I think God frowns on me working in my garden? No. When I have a hoe in my hand, alone in the garden, (gee...that sounds good...someone should make a song of that...) my body is working but most often my mind is on God. It's a time for communion and fellowship...for me. For someone else, their special time with God might be fishing, spending time with their family or building something. Or it might be just sitting quietly reading The Word or praying. I think different people have different ways of honoring God. Look at the children of Israel: there were various craftsmen who constructed the tabernacle. Each did their work to honor God. And it was beautiful to Him.
I do think we should set aside the first day of the week, which under this calender system (and who gives a hoot if we are under a Roman Calender!) happens to be Sunday. I do think we should attend church on that day because Scripture tells us that day is holy (see H6942 above). After church, what we do is our own personal expression of honoring God. I'm a wife and mother. I honor God by taking care of the husband and children He gave me. I honor God by enjoying the horses He gave me and riding through His creation which He also gave me. I don't think there has ever been a time when I have been in the woods that I haven't thought at least once how magnificent and wonderful God's world is. I might work in the garden, or visit with friends. All of which, I believe honors God...if I approach it the correct way.
Back to the original question now: "Is Keeping the Sabbath Necessary for Salvation?" No. We have already determined in other discussions that there is only one thing necessary for Salvation: Jesus and belief that he is The Son of God who died for the forgiveness of our sins, was raised from the dead and now sits at the right hand of The Father waiting to return and take all who believe in him home. But...ask the question a different way: "Is Salvation Necessary for Keeping the Sabbath?" Yep. The very first way we honor God is to believe He is who He says He is and believe what He says. He said we are sinners. He said we needed a Savior. He said He sent His Son as a perfect Sacrifice for those sins. He said we are forgiven and made righteous through that sacrifice of His Son. If we believe all this and the rest of His Word, then we are honoring God...not only on the Sabbath but every day of our lives. And since he said we should honor Him by giving Him the firstfruits of everything, then we should give Him the first day of our week. Look again....
Rom 11:16 For if the firstfruit be holy, the lump is also holy: and if the root be holy, so are the branches.
Do you want the rest of your week to go smoothly? Honor the first day. If the first day is holy then the rest of the week will be, too. In our finances, all God asks is that we give Him His 10%. We get to keep the other 90%. Of our weekly time (one day to be holy and for Him), all God asks is 14.285714285714285714285714285714 %. I also think we should give him the first part of the time of our day: 1 hour would be 04.1666666666666666666666666666667%. 10% of our day would be 2.4 hours. What's the big deal? I mean, you woke up this morning. God has brought you through the night. He has given you the very breath your are breathing and the air you breathe. He has given you His Son! All this seems a small price to pay for all God has given us. But...tha's a Father for ya'. Always giving and asking for so little in return.