I have just completed writing a book: All The Commands of the Old Testament (SIBI, $10). God gave these 2,000+ commands to His people. Most of these commands apply only to the children of Israel, from Moses until Christ’s death on the cross. Christians today are instructed to read the old law of Moses for patience, comfort and hope (Rom 15:4), though we are not obligated to obey those laws unless they are repeated in the New Covenant (like 9 of the 10 commandments). The old law was “nailed to the cross,” “canceled,” “taken away” (Col 2:14).
Some Old Testament laws seem strange and obsolete to us today. For example, consider the laws about testing a wife who “goes astray and is unfaithful” to her husband (Numbers 6). Under Moses’ law, a strange test for her proved her guilt or innocence. If proven guilty, she was “accursed.” However, in both the old and the new testaments, marital faithfulness until death, clinging with one’s partner, is required (Gen 2:18-25). I Cor 7:10 says “A wife must not separate from her husband.” Most Bible scholars consider separation to be equivalent to divorce, even when no legal document is sought (cf McGuiggan, Commentary on I Cor 7 and G. Music, Separation Is Sin, etc).
The same marriage laws have continued from the Garden of Eden (Gen 3:15-19) throughout the Patriarchal, Jewish and Christian ages (Heb 9:15; 10:9-10). Marriage is still binding until separated by death (Rev 22:18-19). The Judgment Day will reveal all when the “books are opened!”