Why is Christ considered to be our Sabbath?

In Hebrews 4, we learn that Christ is our ultimate Sabbath rest. The Sabbath under the Old Covenant was a shadow pointing to the true rest found in Christ, where faith in His completed work grants believers relief from striving to meet the Law’s requirements for salvation. Unlike the Old Covenant's observance of a physical day, the New Covenant invites believers to rest in Christ Himself, who has completed all work necessary for salvation. In Him, we find spiritual refreshment and the assurance that we stand justified before God.