- The first time God blesses anything or anyone is when God tells the newly-created sea creatures and birds to "Be fruitful and multiply and fill" their respective realms (Genesis 1:22).
- God then creates mankind in God's image and blesses them likewise, saying, "Be fruitful and multiply and fill the earth" (Genesis 1:28). But it's additionally stated about mankind that they were made "male and female" (Genesis 1:27). This may simply be a statement about the human creature, or an affirmation that both men and women are made in God's image. But it could also suggest or imply that "male and female" reveals something about God's nature or about mankind's relationship with God.
- God says that "the man" (i.e., the male) was in a "not good" state when he was "alone" (Genesis 2:18). God remedied this by making for him a female counterpart, one with whom he (and she with him) could become "one flesh." While ANE (Ancient Near East) scholars like Frank Moore Cross say that to "become one flesh" in Genesis 2:24 refers to marriage creating a kinship bond, Jesus' and Paul's reference to the verse in the context of their discussing divorce and adultery (Mark 10:2-9) and sex with prostitutes (1 Corinthians 6:16) seems to take "become[ing] one flesh" in Genesis 2:24 to mean the male-female sex act.
- Paul in Ephesians 5:22-33 likens the relationship between a man and a woman in marriage to the relationship Christ has with his church.
- This man-woman/Christ-church marriage relationship (perhaps first alluded to in the parable of the wedding feast - Matthew 22:1-14 and parallels) is finally and most fully realized in Revelation 19:7-9 and Revelation 21-22 with respect to the bride, the wife of the Lamb, the New Jerusalem.
Therefore I think it's difficult for the church to find biblical justification for "blessing" same-sex unions or according them the same status as male-female marriages. It's not that two same-sex people can't love or commit to or complement (at least in non-genital ways) each other, but that male-male and female-female do not seem to accord with a significant biblical metaphor, which may in fact be a heavenly reality of which human male-female marriage serves as a copy or shadow (Hebrews 8:5). I.e., same-sex unions are problematic because they may not be proper icons of Christ and the church.