The general impression that most Americans have is that all organized religious groups condemn the idea of same sex marriage, but nothing is farther from the truth!
Certainly, in a broad sense, the following groups DO oppose gay marriage with great vehemence: Evangelical Christians, the Catholic Church, Mormons, Orthodox Jews, African American Protestants, and Hispanic Pentecostals.
However, at the same time, the following groups often support the concept of gay marriage as legitimate: Mainline Protestant groups, including Episcopalian, Presbyterian, Methodist, United Church of Christ, and Lutherans, although all have splits on the issue; some rebel Catholic groups; and Reform Judaism.
It is clear that clergy were intimately involved in the passage of gay marriage in the New York State legislature, convincing a few Republicans to switch over to support, which would make the difference between victory and defeat.
Religious groups are divided on the subject, so one cannot say that those who speak for God are uniformly opposed, and progress has been made over the past decade in changing many religious groups to have an open mind and a tolerant view of promoting commitment and love outside the mainstream!