I don't believe you commit a sin if you don't keep the Sabbaths for that was then, this is now. What God is showing you personally is that if you create a law for yourself, whatever that may be, such as to do no work on Saturday's, if you break it even once, let it prove you are a sinner, among other ways to show you are a sinner in need of salvation. Salvation is not going to be received if you try to keep the Sabbath, thus rejecting Christ for the Sabbath points to the rest of the Holy Spirit indwelling.

What does Paul teach concerning the Sabbath? He maintains that the Sabbath is a thing that has passed away: “having blotted out the bond written in ordinances that was against us, which was contrary to us: and he hath taken it out of the way, nailing it to the cross . . . Let no man therefore judge you in meat, or in drink, or in respect of a feast day or a new moon or a sabbath day: which are a shadow of the things to come; but the body is Christ’s” (Col. 2.14,16-17).

The burden of the proof is on you to show otherwise.