This can be a difficult issue. Believers want to show friendship, but we’re wary of seeming to condone the unbiblical aspects of a wedding ceremony in another religion.
As a starting point in any decision-making process, we should pray for wisdom (James 1:5). What does God say in regards to whether or not you should attend the ceremony?
In general, though, if a believer is invited to a marriage ceremony, he or she should feel free to attend. God instituted marriage, and, whether the couple is Christian, Hindu, Sikh, Buddhist, atheist, or some other religion, marriage is honorable in God’s eyes (Hebrews 13:4). As long as the marriage is between a man and a woman, it is as God intended. Attending the ceremony is a matter of supporting the bride and/or groom; it’s not necessarily a stamp of approval on another faith.
In some cultures, elements of paganism are part of the wedding ceremony. A traditional Bengali wedding, for example, includes prayers and offerings made to an idol. If attending a wedding requires a believer himself to perform a pagan ritual, then he should honor God rather than man (Acts 5:29). In most cases, however, a Christian can simply attend and not be involved in the sacrifices to false gods. There is also the possibility that others will interpret a Christian’s presence there as giving “approval” to what is taking place. Again, this is a situation that demands prayer and godly discernment.
Jesus’ prayer in John 17:15-18 contains a principle that may help: “My prayer is not that you take them out of the world but that you protect them from the evil one. They are not of the world, even as I am not of it. Sanctify them by the truth; your word is truth. As you sent me into the world, I have sent them into the world.” Christians are in the world, sent by Jesus Himself, but we are not of the world. We are an infusion of light in a dark place (Matthew 5:16). The goal is not to separate totally from the people and events of a culture, but to be preserved from evil.
The friendships we make with those of another religion may plant seeds that someone else may water, and God may later bring the fruit (1 Corinthians 3:6). To be asked to take part in a wedding is an honor and a privilege. We should use everything that comes our way to bring glory to the Lord.