Those who insist that we are to keep the Sabbath are attempting to hold onto the Sinai covenant of bondage.
We are part of the Promise made to Abraham, before Mount Sinai.
Abraham was not commanded to keep a Sabbath.
Col 2:16 Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days:
Col 2:17 Which are a shadow of things to come; but the body is of Christ.
Gal 3:16 Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.
(The Abrahamic Promise was made to Christ.)
Gal 3:17 And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.
(The Sinai law was "added" 430 years "after" the Promise to Abraham.)
Gal 3:18 For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise.
(The inheritance comes through the Promise to Abraham, not the Sinai covenant.)
Gal 3:19 Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.
(The Sinai covenant was "added" "until" the Seed could come to whom the Promise was made, which is Christ.)
Attempting to keep a "Sabbath" of either Saturday or Sunday is not scriptural.
Every day of the week is suitable as a day of worship in the New Covenant.
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We keep the Lord's Day as a reminder of the first fruit of the New Covenant - the day of His resurrection, not necessarily as the new sabbath day. Do you believe that the only reason people celebrate on Sunday is due to it being the "new sabbath"? That is not the reason for many worshiping corporately on Sunday. That said, of course we can worship on any day of the week. That doesn't mean it isn't important to celebrate the day of or Lord's resurrection though. There are reasons the early church celebrated the Eucharist on the Lord's Day. I don't believe it was directly a result of changing the sabbath though.
That said, as a fulfillment of the Old Covenant - keeping the Lord's Day as a holy day is a good thing to do imho.
Check out some writings from the early church fathers. Note that the early church recognized Sunday as the day of our Lord's resurrection. I don't expect you to take these external writings as being authoritative, but even when not accepted as authoritative in any manner, it is helpful for historical context:
Saint Ignatius writes,
Those who we brought up in the ancient order of things have come to possession of a new hope, no longer observing the Sabbath, but living in the observation of the Lord's Day...
Saint Justin Martyr writes,
Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Savior on the same day rose from the dead.
2nd Century A.D. 120
Saint Barnabas writes,
“We keep the eighth day with joyfulness, the day on which Jesus rose again from the dead.” Chapter XVII.
3rd Century About A.D. 250
The Apostolic Constitution:
“On the day of our Lord’s resurrection, which is the Lord’s Day, meet more diligently.”
And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them.” Acts 20:7.
“I was in the spirit on the Lord’s Day.” Rev. 1:10.
All this said - Sabbath keeping - while related to sola scripura - is a bit off topic and probably should be in a separate thread than this one.
