How do we know the Sabbath law does not apply to Christians?

The New Testament makes it clear that the Sabbath law, as stipulated in Old Testament times, was a command specific to Israel and was tied to their national identity. Colossians 2:16-17 explains that such laws were shadows of things to come, with Christ being the substance. After the coming of Christ, the early church is admonished not to let anyone judge them regarding sabbaths, as these were a part of the old covenant, which has been made obsolete (Hebrews 8:13). Therefore, Christians are not under the Sabbath law but are encouraged to find their rest in the completed work of Christ.