(This posting won’t make much sense unless you are familiar with the posting on “Sex in Heaven” here.)
But what about Genesis 6? Doesn’t it describe “angel sex” and how this is so broadly condemned?
Genesis 6:1-2 says that “sons of God” (angels) came and married the daughters of men, conceived children by them, and this was one of the proximate causes of the Great Flood; God was obviously not pleased with such angel behavior.
Well, perhaps. The identification of these “sons of God” as angels is one possibility, but scarcely the only one; an argument can be made that “sons of God” refers rather to those men on the earth who still worshipped God appropriately (as opposed to “daughters of (wicked) men”), and therefore this passage was foreshadowing in some ways the sort of mixed Israelite-Canaanite marriages that would become a problem in Exodus and all the way through Ezra (ch 10) and Malachi (2:11). Even if one allows that these are angels, the offense is not necessarily that they had relations or even children, but that this was a mixing of angelic and human realms. It was, in other words, an illicit attempt to bridge these two worlds, of the same sort that was attempted with the building of the tower of Babel (in an effort to reach heaven). This same concern with “hybrid beings” possibly underlies Mosaic prohibitions against mixing fibers in clothing and seeds in fields (Lev 19:19) and other sorts of hybridization. Some have even argued that this is the ultimate reasoning behind the prohibition against eating shellfish: they’re animals that aren’t fish (lacking fins and scales and sometimes having legs) but aren’t quite land animals (living in the water). This separation between heaven and earth did not exist before the Fall, and will again be eliminated in the eschaton, but these are matters beyond what we’re concerned with here. This passage can only be made to completely prohibit “angel sex” again with dragging in assumptions foreign to the text, or by assuming that the conditions of Gen 6 will exist eternally. (cf Jude 6)