10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.Paul said that one man regards everyday the same, and another regards a day as he pleases. Basically Paul said not to judge anyone who regards to set aside a particular day.
Christ fulfilled the Law in it's entirety, including the Sabbath Day. He gave us liberty from the work of the Law.
The New Testament marks the end of works as demanded by the Law, Christ is our Sabbath, our rest is found in Him.