Here Dr. Frank Turek answers one of the least-well explained aspects of believers transition into the New Covenant under Christ, post Jesus Resurrection, concerning the Sabbath: https://www.youtube.com/watch?v=PaXQEKYOncM

And for a MUCH more detailed and panel of Christian scholars look at the issues of the OT Sabbath, whether their still IS a Sabbath, and whether it's Sunday, and whether or not Christians must observe a Sabbath at all, I would highly recommend this excellent book, edited by D.A. Carson: "From Sabbath to Lord's Day: A Biblical, Historical and Theological Investigation": https://www.amazon.com/Sabbath-Lords-Da ... 112&sr=8-1 - this book offers a fascinating deep dive that has much historical, theological scholarly analysis surrounding theses questions. Note, there are used copies of this book that can be found online considerably cheaper.