2 On the seventh day God had finished His work of creation, so He rested from all His work. 3 And God blessed the seventh day and declared it holy, because it was the day when He rested from all his work of creation. -Genesis 2 :2-3 NLT
God finished all His work on the 6th day, so why did He need to have a 7th day, and called this day SABBATH, a day of REST? This day He placed great significance in it. He blessed it and incorporated it into His commandments as one of the laws He expected His children to live by. A day He dedicated to Himself (Exodus 20:8-11)
The Lord says, 12 And I gave them my Sabbath days of rest as a sign between them and me. It was to remind them that I am the lord, who had set them apart to be holy. 20 and keep my Sabbath days holy, for they are a sign to remind you that I am the lord your God -Ezekiel 20:12 & 20
So, the day of REST is a day that the Lord set apart as a reminder to us that He is our God and we are His. It is a sign of distinction, a sign that we are set apart by Him for Him. So then, observing the Holy Sabbath separates or identifies you as set apart by and for the Lord. Therefore, the 4th commandment is a law of distinction.
However, with the coming of Jesus God said, ‘I will put my laws in their minds and write them in their hearts. I will be their God and they shall be my people.’ -Hebrews 8:10. This word then became true as God set a new covenant with the people, because He found fault with the old covenant. The new covenant became Jesus, meaning that Jesus became our law of distinction.
Jesus being the new covenant however, did not take away the Sabbath, as Jesus also says, 17 “Don’t misunderstand why I have come. I did not come to abolish the law of Moses or the writings of the prophets. No, I came to accomplish their purpose.
-Matthew 5 :17
However, His coming changed people’s rest from a day to Jesus himself. He became our place of rest, our Holy Sabbath.
He continues to say in Matthew 12:12 “… It is lawful to do good on the Sabbath”. He himself as our Holy Sabbath stands only for good. So, we do good no matter what day because our rest is no longer physical, but spiritual in Him who redeemed us.
Revelation 7:9 says …
9 After this I saw a vast crowd, too great to count, from every nation and tribe and people and language, standing in front of the throne and before the Lamb. They were clothed in white robes and held palm branches in their hands.
And the book of Exodus 15:27 says …
27 After leaving Marah, the Israelites traveled on to the oasis of Elim, where they found twelve springs and seventy palm trees. They camped there beside the water.
So, the book of Revelation tells us that we will be identified as those that belong to God in the last days by palm branches in our hands, as a confirmation of our rest in Jesus, our law of distinction
However, if you apply this law by observing it on a day, you abide to the law of whomever set that day as the day of rest e.g. Sunday set by the Roman Catholic or Saturday set by the Lord. Therefore, you do not have to physically abide to the law, but you are expected to abide to it spiritually under the new covenant.
It is not to say do not worship God on Sunday. Every day, every hour, every minute and every second is set for the continuous chain of worshiping God. When you are not, someone else is at whatever time.