The sabbath is part of the old law that was nailed to the cross. If you go back and keep any of that law, you have to keep all of it. And after the destruction of Jerusalem, and especially the temple where the sacrifices were offered to atone for sin, there is not a way to keep the law even if you wanted to do so.
In Titus 2:11-14, our salvation is described as being trained by grace to do what is godly, righteous, and good, and to renounce doing what is ungodly, which is what God's law was given to instruct us how to do. Furthermore, verse 14 does not say that Jesus gave himself to end any laws, but rather it says that he gave himself to redeem us from all lawlessness and to purify for himself a people for his own possession who are zealous for doing good works, so if we believe in what Jesus accomplished on the cross, then we will become zealous for doing good works in obedience to God's law (Acts 21:20) and will not return to the lawlessness that Jesus gave himself to redeem us from.
If you believe that God's law was given for our own good in order to bless us (Deuteronomy 6:24, 10:12-13) and if you believe that God can be trusted to guide us in how to rightly live, then obeying the whole of God's law should not be considered to be a bad thing. On the contrary, David said repeatedly throughout the Psalms that he loved God's law and delighted in obeying it, so viewing obedience to it with anything less than delight is incompatible with the view that the Psalms are Scripture. Paul also delighted in obeying God's law (Romans 7:22), so he was on the same page as David. It is not as though the preferable alternative to living in obedience to God's law is to living in complete disobedience to it and refusing to repent. However, that was not the whole law that was being referred to.
When the Israelites were in exile in Babylon, the condition for their return to the land was to first return to obedience to God's law, which required them to have access to a temple that they didn't have access to while they were in exile, but they were nevertheless faithful to obey all that could be obeyed.
Besides which, going back to the old law causes one to fall from grace.
5 Stand fast therefore in the liberty by which Christ has made us free, and do not be entangled again with a yoke of bondage. 2 Indeed I, Paul, say to you that if you become circumcised, Christ will profit you nothing. 3 And I testify again to every man who becomes circumcised that he is a debtor to keep the whole law. 4 You have become estranged from Christ, you who attempt to be justified by law; you have fallen from grace.
All throughout the Bible, God wanted His people to repent and to return to obedience to His law, and even Christ began his ministry with that message, so it would be absurd to interpret this passage as Paul warning us against obeying God and saying that we will be cut off from Christ if we follow Christ. Furthermore, it wouldn't make sense to fall from grace by obeying God as if obedience to God were somehow a negative thing. In Psalms 119:29, David wanted God to be gracious to him by teaching him to obey His law, so that is what being under grace looks like, and it wouldn't make sense to think that he wanted God to be gracious to him by teaching him how to fall from grace. Likewise, in Romans 1:5, do you think that we have received grace in order to bring about our fall from grace? Or is does Titus 2:11-14 describe our salvation as being trained by grace how to fall from grace?
Jesus gave us new commandments. Thou shalt not murder became love your brother because hating him is murder. Thou shalt not commit adultery became don't even lust after a woman when you are married to another.
If Jesus had given us brand new commandments, then he would have sinned in violation of Deuteronomy 4:2 and disqualified himself from being our Savior. However, even if he had been giving brand new commandments, then it would have at the very least still been inclusive of the Mosaic Law because if we don't even hate our brother, then we won't murder, and if we don't lust after a woman, then we won't commit adultery. However, the reality is that we are commanded not to hate our brother in Leviticus 19:17 and the command against looking at a woman with lust in our hearts is just the correct application of the 7th and 10th Commandments against adultery and coveting in our hearts, so Jesus was not teaching any brand new laws in violation of Deuteronomy 4:2.
And the new Sabbath is "the Lord's Day" when all of the church is supposed to meet, give their alms and worship God in truth and spirit.
In Greece, their word for Sunday is still the word meaning "The Lord's Day." The first day of the week. It is we who seek to enter into his rest by obeying the new covenant's commands and realizing that Christ completed the old covenant and nailed it to the cross.
Jews traditionally did not handle money on the Sabbath, so they would wait until the close of the Sabbath on the 1st day of the week to collect offerings. Jesus set an example of keeping the 7th day holy and the New Covenant does not involve refusing to follow him, but rather it still involves following God's law (Jeremiah 31:33).
