There are two covenants.
The Old Covenant was made with Israel at Sinai after Moses brought them out of Egypt.
Under the Old Covenant Israel was commanded to keep the seventh day of the week in a special way.
God’s days go from sundown to sundown.
Genesis 1:5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
The seventh day, called the Sabbath, begins at sundown on Friday and ends at sundown on Saturday.
Exodus 20:10 But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: 11 For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it.
Exodus 31:14 Ye shall keep the sabbath therefore; for it is holy unto you: every one that defileth it shall surely be put to death: for whosoever doeth any work therein, that soul shall be cut off from among his people. 15 Six days may work be done; but in the seventh is the sabbath of rest, holy to the LORD: whosoever doeth any work in the sabbath day, he shall surely be put to death. 16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.
Exodus 35:2 Six days shall work be done, but on the seventh day there shall be to you an holy day, a sabbath of rest to the LORD: whosoever doeth work therein shall be put to death. 3 Ye shall kindle no fire throughout your habitations upon the sabbath day.
Israel failed to keep the Covenant and so God promised a New Covenant which would be different from the Old.
Jeremiah 31:31 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: 32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: 33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. 34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
The writer to the Hebrews explains:
Hebrews 8:8 For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah: 9 Not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they continued not in my covenant, and I regarded them not, saith the Lord. 10 For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people: 11 And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest. 12 For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.
The New Covenant replaces the Old.
Hebrews 8:13 In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.
Jesus Christ is the mediator of the New Covenant.
Hebrews 12:24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.
The Law of Moses was a schoolmaster to bring us to Christ.
Galatians 3:24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
In Christ we are no longer under the schoolmaster (the Law of Moses).
Galatians 3:25 But after that faith is come, we are no longer under a schoolmaster.
When we believe the gospel and are baptised into Christ we come under the New Covenant.
Jesus Christ fulfilled the Law in its entirety. He was the only one who could. In fulfilling it, he took it out of the way.
In Christ we are ‘dead’ to the Law of Moses.
Romans 7:4 Wherefore, my brethren, ye also are become dead to the law by the body of Christ; that ye should be married to another, even to him who is raised from the dead, that we should bring forth fruit unto God.
Galatians 2:19 For I through the law am dead to the law, that I might live unto God.
Circumcision and the rest of the Mosaic ordinances (including Sabbath observance) no longer apply.
Galatians 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
We are required to obey the commandments of Jesus Christ, not the Law of Moses.
John 15:14 Ye are my friends, if ye do whatsoever I command you.
Jesus commands us to remember him in a particular way
Luke 22:19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me. 20 Likewise also the cup after supper, saying, This cup is the new testament (Covenant) in my blood, which is shed for you.
1 Corinthians 11:23 For I have received of the Lord that which also I delivered unto you, That the Lord Jesus the same night in which he was betrayed took bread: 24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. 25 After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me. 26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord’s death till he come. 27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord. 28 But let a man examine himself, and so let him eat of that bread, and drink of that cup. 29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord’s body.
From this we understand that baptised believers are to share bread and wine in remembrance of Christ’s sacrifice and use the opportunity for self-examination.
We are not commanded to do this on the Sabbath.
We are commanded to do it ‘often’ and no day is specified.
The early Church found it convenient to ‘break bread’ on the first day of the week – that is – Sunday.
Acts 20:7 And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
1 Corinthians 16:2 Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
Meeting on Sunday became the Church tradition.
What we need to remember is that no day is specified but it must be done ‘often’.
The first day of the week is not the Sabbath. It has nothing to do with the Sabbath.
We can meet to share bread and wine in remembrance of Christ’s sacrifice on any day.
The important thing is to do it regularly.
The ‘carnal ordinances’ of the Law of Moses are no longer in force for those who believe and obey the gospel.
We are not under the Old Covenant and the Law of Moses, which cannot save us.
Galatians 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
Galatians 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
We are under the New Covenant and live by the commandments of Jesus Christ and his apostles.
The commandments of Christ are the rock upon which we build our faith.
Luke 6:46 And why call ye me, Lord, Lord, and do not the things which I say? 47 Whosoever cometh to me, and heareth my sayings, and doeth them, I will shew you to whom he is like: 48 He is like a man which built an house, and digged deep, and laid the foundation on a rock: and when the flood arose, the stream beat vehemently upon that house, and could not shake it: for it was founded upon a rock. 49 But he that heareth, and doeth not, is like a man that without a foundation built an house upon the earth; against which the stream did beat vehemently, and immediately it fell; and the ruin of that house was great.
Paul tells the Colossians:
Colossians 2:16 Let no man therefore judge (krino – condemn) you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days.
Sunday and the Sabbath: https://www.thisisyourbible.com/library/show/176
I hope you find this helpful.