When God created Eve for Adam, He forever established the definition of marriage for humanity: one man, one woman, joined together for as long as they both lived. Mankind quickly twisted that standard by adding polygamy, concubines, and divorce. Now we're seeing the unbiblical addition of marriages between two people of the same gender.
Should a Christian attend the wedding of a couple of another faith?
But nowhere does the Bible limit the institution of marriage to followers of God. Marriage is for every people of every nation and religion. And God recognizes the legitimacy of marriages performed in other religions. Christians are free to celebrate the biblical expression of marriage no matter what the faith of the couple.
Often weddings act as a religious service. When this is the case, believers need to have more discernment. If the guests of a wedding are required to participate in an unbiblical religious act, the wedding should be avoided. Alternately, the Christian could contact the couple and see if a compromise could be made; it may even be possible to skip the ceremony and attend the reception.
Another question that is more difficult to answer is, "Should a Christian attend the wedding of a believer to a non-believer?" The Bible tells us that we are not to be "unequally yoked," that is, to have a close relationship with an unbeliever. Marriage would certainly apply. For a Christian to marry a non-Christian, then, is usually sin. And for a believer to attend the wedding could be considered endorsing and encouraging that sin. It's a matter for serious prayer and spiritual discernment. But once the wedding is completed, the believer should make every effort to support the marriage. God recognizes the legitimacy of even unwise marriages and calls believers to stay with their unbelieving spouses (1 Corinthians 7:12-14).
There is nothing unbiblical about the marriage of a couple of a non-Christian faith. To celebrate such a joyful occasion is certainly within the rights of their Christian friends. The only questions arise if the attendees of the wedding ceremony will be asked to actively participate in a religious ceremony or act. If there's any doubt, contact someone related to the ceremony and ask.
What does the Bible teach about marriage?
Should Christians date or marry non-Christians?
Can a divorced person remarry?
Biblically, what constitutes a marriage?
Where should we, as Christians, stand on gay marriage?
Truth about Life Decisions