Without citing scripture, you're quoting it out of context. You're applying "it is finished" to Commandment Number 4.
Now one does find rest in Christ, but it is the same way one found rest in Christ BEFORE the Cross. They sought Him early in the morning (King David's Psalms), they had faith in the Redeemer TO Come (before the knowledge was lost about what the Saviour was actually going to do). Now, I am not implying that God got tired, and therefore had to rest. No, God rested purposefully on the Sabbath Day. You also cannot say the Sabbath was not about a specific day or time set aside, because there are zero, I repeat, zero, Scriptures which back you up on that. Specifically in Genesis, we see that God rested and set the day apart for Holy Use. In the Commandments, we see why we keep the Sabbath, because we copy our Creator in character, and in things that we do and do not do. We also find that Jesus states the SABBATH was made for man, not for the Jew. And certainly, not pointing to the Cross. And nowhere do the Scriptures declare that the 7th Day Sabbath had anything to do with the cross. Again, I emphasize turning to Genesis 2:1-3 and Exodus 20:8-11. It was not a SHADOW of something to come. The commandment itself points BACK to Creation week. It is not as the other Sabbaths which do not find their place within the eternal moral law. The other holy days did in fact point to what Jesus would do on the cross.
You cannot apply "it is finished" to the Sabbath Commandment. To do so, you must then apply the EXACT same logic to all the other commandments. All of them, or none of them, as per James 2:10. This is a "grouping" issue. What we are seeing is taking the moral law, stripping out the 4th one, and placing that with the ceremonial law. You simply cannot do that. That is picking and choosing what you can and will obey, and that is what is spoken of again in James Chapter 2 (early on). If you teach obedience to any part of that law, you must obey all of it. There is no picking and choosing.
The Word "Remember" appears within the fourth commandment. It is the only commandment which Christiandom has forgotten to keep. One can see the Creator's wisdom in placing THIS word into that commandment. So, will you say "Remember" the Sabbath, actually means "Forget it"?
So no, Jesus is not "the Sabbath". Jesus is - the Saviour - of those obedient Christians who keep the Sabbath.
I mean no disrespect, but I must point out that the stance that Jesus is the Sabbath, doesn't make any sense. One cannot provide for me a shred of Biblical Text in context that says, "Therefore, Jesus is your Sabbath". Scripture emphasizes keeping God's Commandments, keeping the entire law, and it emphasizes Jesus did not change anything within that lie. It also emphasizes to Remember the Sabbath - TO KEEP IT HOLY. The commandment continues and points out the requirement of resting the seventh day.
Now if you disagree with all that I said, I would like to take another look at simple common sense, and contradictions.
Letter of the Law Commandment Number Six Spirit of the Law
Do not literally murder Thou shalt not kill Do not hate your brother within your heart
As a Christian you keep this commandment quite literally, to the letter, yes? You also have the help of Jesus to keep this commandment within your heart as well. You are therefore keeping the letter of the law, and the Spirit of the law. Let's look at another commandment
Letter of the Law Commandment Number Seven Spirit of the Law
Do not literally commit adultery Thou shalt not commit adultery Do not look after a man or woman with lust
As a Christian you keep this commandment also quite literally. You also have the help of Jesus to keep this spiritually as well. You can do that with EVERY single commandment and find that you keep the letter and the spirit of the law. Now, think about commandment number 4. Does it make, any sense, whatsoever, to claim to be keeping a law spiritually, if you quite honestly refuse to keep it literally? Think about that. How does that even make sense? How can you claim to keep the Sabbath, even claiming that Jesus is your Sabbath, if you do not "Rest the Sabbath Day According to the Commandment"? Even John the Revelator was found keeping the LORD's day in Revelation 1:10. What is the LORD's Day? The World refers to it as Sunday. I do not, I let Scripture say that Jesus is LORD of the Sabbath Day, and that it is HIS Holy DAY (Isaiah 58:13-14). It's an absolute contradiction. We keep literally and spiritually all the other laws. There is not a Scriptural reason that the same logic does not apply to the 4th Commandment. The 4th Commandment testifies of itself that it would be later forgotten. And again I repeat, keep the whole law, Jesus did not change the law, and we are to REMEMBER to keep the Sabbath Day.