In discussions of same-sex marriage, people often cite the Bible, which describes marriage as being between a man and a woman. However, God can change customs, even ones that seem fundamental.
I would ask people to read Acts 10 and 11, in which God tells Peter that the word of Jesus is not only for the Jews, but he is also to bring it to the Gentiles. It's hard for us now to understand how shocking this was at the time (but see Acts 10:28).
Peter was hungry when he fell into a trance. He had a vision of a sheet let down from heaven, with all kinds of birds and beasts, and a voice told him to kill and eat. But Peter answered: Certainly not, Lord; I have never yet eaten anything profane or unclean. Again, a second time, the voice spoke to him, `What God has made clean, you have no right to call profane.' (Acts 10:14-16)
After receiving this vision, Peter accepted an invitation to preach to a family of Gentiles. When they were converted, he baptized them and said, "Could anyone refuse the water of baptism to these people, now they have received the Holy Spirit just as much as we have?" (Acts 10:47)
When he was challenged by the apostles and other Jewish believers, Peter told them about his vision and said, "I realized then that God was giving them the identical thing he gave to us when we believed in the Lord Jesus Christ; and who was I to stand in God's way?" (Acts 11:17)
You may ask, "When did God tell you that gay marriage is OK?" Look back at this story and ask, "When did God tell Peter that it was OK to preach to Gentiles?" As so often happens, the lesson is taught in symbols, which we must figure out. But to paraphrase Acts 10:47, "Could anyone refuse the sacrament of marriage to these people, now they have made a promise of love and commitment just as much as we have?"
A number of years ago, when my friends Steve and Jim asked for our church's blessing on their union, I was deeply troubled. A same-sex marriage just didn't seem like the same sort of thing as a "real" marriage. But then I went through my own marriage vows, word by word, and asked myself, "What part of this promise do I feel it would be wrong for Steve and Jim to make to each other, before us and before God?"
I could find nothing wrong. I supported their marriage, and it was the right thing to do. Only much later did I remember Acts 10 and 11.
What is new and strange is often troubling, but it may still be right. Years from now, we will look back and wonder what all the fuss was about.
If you struggle with this question, read Acts 10 and 11. Get to know a specific committed same-sex couple, and ask yourself how you, or society, is harmed by them making and keeping a lifetime promise to each other. Pray for guidance, and you will get it.
A friend drew my attention to Matthew 10:5-6, where Jesus is instructing his disciples: These twelve Jesus sent out, instructing them as follows: "Do not turn your steps to pagan territory, and do not enter any Samaritan town; go rather to the lost sheep of the House of Israel."
It seems, then, that teaching the Christian message to Gentiles (including most of us), is not only based on Peter's interpretation of the word of God conveyed in his dream, but directly contradicts the instructions that Jesus himself explicitly gave to Peter and the other disciples.
It's hard to avoid the conclusion that God can change His mind (or at least his instructions to us) about what is and is not allowed. Furthermore, the word of such a change can come to an individual, directly from God, not through a bureaucratic process.