So, because I believe in Jesus I follow what He says. And Jesus says to follow the will of his Father in Heaven. And His father said to keep the 7th day holy.
Your response is an overly simplistic answer that, while on its own merits sounds true, is actually incorrect within context.
If I take that at face value, then it would reason to follow that you also sacrifice animals according to the specifics that God commanded. Do you do that? Do you offer burnt offerings of a lamb, a ewe, and a ram once a year? Do you observe all the dietary laws? It sounds like you say you do, but to be honest I don't know anyone these days who sacrifices animals. You really do?
If I believe in exercise I go to the gym, I don't sit around all day. If I believe in vegetarianism I don't eat meat, I follow what vegetarianism means. If I believe in Jesus I do what Jesus says. How can you say you believe in Jesus if you don't follow His commandments? And isn't that how we are saved? By believing in Jesus? Even the demons believe, but they don't believe in. Read what James 2 is actually saying:
If you believe in exercise and go to the gym it is because you believe that by works you will gain something. That is not a good analogy for God's Grace and Mercy; in fact, it's the opposite, it's an analogy for God's Law and His Justice.
Here's a better analogy. Do you believe that a husband must buy his wife gifts in order to earn her love? If you believe this, then the kind of "love" you believe in is a phony, purchased, earned love. If you believe in true, merciful, unconditional love then you would believe that a husband does NOT NEED to buy his wife gifts to have her love. If she truly loves him, he could never buy her a gift ever in their lifetime together and she would love him just the same. Of course, if he truly loves her, his actions would probably be that he would buy her gifts, but would he NEED to? Absolutely not. And if he didn't it wouldn't have bearing on their love for each other.
To take that analogy further, what if a woman truly loved her husband but he came to her with a gift and after giving it to her he said, "I hope you love my gift enough that you will continue to love me!"??? I think the wife would be insulted that the husband bought her a gift thinking that it somehow enhances her love for him.
Likewise with observing the Sabbath. I think it's an insult to Christ to say, "Lord, I know you have redeemed me from sin once and for all and that you have provided us an eternal rest from labor under the Law, but I'm STILL gonna observe a Sabbath day, aside from you being my rest, and use that day to rest from the law which you have already provided me rest from, because I will feel better or I will think it pleases you for me to duplicate what you have done for me (and even better than I could do on my own)."
How is observing the Sabbath day glorifying to God? It is insulting. It is telling the Lord that His rest that He provides us is not enough and that we need to go back to the old stop-gap He provided before we received His Perfect Gift.
James 2
19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
20 But wilt thou know, O vain man, that faith without works is dead?
21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
22 Seest thou how faith wrought with his works, and by works was faith made perfect?
23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
24 Ye see then how that by works a man is justified, and not by faith only.
25 Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent
them out another way?
26 For as the body without the spirit is dead, so faith without works is dead also.
It's true our faith will bear itself out in our works, but remember that that's the correct order. Faith --> Works. Works do nothing for us. Works are for us at best a sign to ourselves and others that our faith is real. Works do not increase God's Glory. We cannot add to Him, He is perfect. Works are simply our expression of our faith. We cannot receive salvation by works because under works we are already condemned, no matter how many good works we do now that we are saved. Our salvation comes from our faith in God's Grace.
So to sum up, I DO "observe the Sabbath", but I do so in the correct way that God's Word teaches us, which is that Christ is our Sabbath, i.e. that the Sabbath is FULFILLED in Christ's life and work. I observe that the Sabbath was once a day, back in the times of Law-based salvation (which included animal sacrifice, burnt offerings, rituals, temple worship, priests, etc.) and now Christ has fulfilled everything that the Law once held over us. Christ is now our salvation and we are free from animal sacrifice, burnt offerings, rituals, temple worship, a priesthood (WE have priesthood ourselves), and the Sabbath DAY.
People who are observing the Sabbath are inconsistent if they are not also following God's commandments about atonement through sacrifice and temple worship and dietary laws - and if they're doing those things, they are following Judaism, not Christianity, because they are denying Christ's saving work on the cross.