1. -- What is this passage really about? If you answered “marriage”, I’m afraid you are mistaken, not understanding the Scriptures nor the power of God. As the text says, this passage is about resurrection, and that this is taught in Scripture and reflects the power of God.
2. -- Does this passage mean there is no marriage in heaven? As our Mormon friends will point out, strictly the passage does not say “there is no marriage”, but “they will neither marry nor are given in marriage”. Though I would quibble with their subsequent reasoning, I think they are correct: the passage could, at least in theory, allow for an earthly marriage to continue.
3. -- What kind of marriage are we talking about here? Where I would quibble more with the Mormons is that this passage isn’t really about “marriage” as we conceive of it. The Sadducees were concerned about what is technically known as “levirate marriage”: the custom of a man ‘marrying’ his late brother’s wife in order to raise up children in his brother’s name. Notice there is no mention of an existing wife who might not want to share her husband nor any mention of love nor “soul mates”. Put bluntly, the reason the man is marrying this woman is to have enough episodes of intercourse to get her pregnant with a child who can carry on her dead husband’s name. I presume it’s obvious that this is a generally different sort of marriage than we conceive of today, however common it may have been in Jesus’s day (and there’s a fair bit of debate as to how often it really occurred even then). Given this, the Sadducees’ question is more silly than vexing: Mosaic covenant concerns about land inheritance are presumably not going to be an issue in an environment where there is no strife over land and inheritances.
4. -- Jesus points out that we will “be like the angels”: so what do we know about the social lives of angels, exactly? Most people reflexively assume this means nothing like sex or anything like it. I humbly suggest this probably owes more to a mashup of Stoic (or even Gnostic) deprecation of the body and some leftover Victorian delicacy (the people who brought us angels who look like this) who are about as far from sexual as possible. I, for one, don’t claim to know much about angels or their relations with one another, except that whatever they do is in accord with their created nature as not generally bound by our physics and materiality. Indeed, if you’ve read any of Teresa's "Autobiography" (e.g. XXIX, 17), the beatific vision can be suspiciously sensual. I doubt she knew any more than the rest of us, but she wasn't being a heretic in describing this way, either.
All of this brings out a common difficulty people have in reading the Bible: it often times is annoyingly deaf to the questions we ask it. Here’s just a sample of these questions, some more controversial than others:
- Will my beloved dog Fifi make it to heaven, hopefully without her annoying tendency to piddle on the carpet when excited?
- Will I get to review my life as I lived it?
- Will I be able to listen to some rock n roll (not the devil-worshiping kind, of course)? Will I be able to watch “Star Wars” on a 108” screen in high def?
- Will I get to watch the family I left behind, like grandpa does with Billy in “The Family Circus” (and am I the only one who finds this a little creepy?)?
- How exactly do we experience God between our deaths and the resurrection? We will be “with Christ” (Phil 1:23), but what does that mean exactly?
- What specific sorts of events will precede Christ’s return?
- Is an electrified praise band more or less pleasing to God than an organ?
- How exactly did the Bible’s authors receive their inspiration? Did they even know what they were doing, and how did God oversee the formation of the Bible?
- Is Gandhi in hell? Why or why not? And what about (fill in the blank with anyone who was not especially and obviously saintly)?
- What about homosexuality? And aborted babies? And how exactly does Jesus's death on a cross 2000 years ago affect my sins today?
Some are obviously more important than others, but I’ve seen attempted answers to all of these and more. The only reliable thing about these questions is that the answers tend to be believable in approximately inverse proportion to how sure the answering authority is in his conclusions. The ghosts of Harold Camping and Lindsey's "The Late Great Planet Earth" live on.
So, in the grand scheme of things, will we have sex in heaven? I don’t know. Jesus really only answers this question if you start dragging in a bunch of extra-textual assumptions, at least some of which are silly and probably even contrary to otherwise well-thought out Biblical theology. I admittedly find it hard to believe that God made a mistake when he invented sex and it will all go in the dustbin on Christ's return. I also find it hard to believe that those, er, parts of our bodies will be solely decorative in the resurrection, but deciding what a uterus in a resurrected woman is good for is speculation of the airiest sort.
All of this reminds me a little of a classic CS Lewis quote:
“I think all Christians would agree with me if I said that though Christianity seems at first to be all about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into something beyond. One has a glimpse of a country where they do not talk of those things, except perhaps as a joke. Everyone there is filled full with what we should call goodness as a mirror is filled with light. But they do not call it goodness. They do not call it anything. They are not thinking of it. They are too busy looking at the source from which it comes. But this is near the stage where the road passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can see further than mine." ― Mere Christianity
Most of these questions are only answered "where the road passes over the rim of our world." I think there can be helpful speculation on some of these, if for no reason other than that they force a person to confront what they really believe about these assorted topics and work through some of the implications. If the implications of a way of thinking about a question don't lead to Christ as king of heaven, then that manner of thinking will be 'revealed with fire, and the fire itself will test the quality of each man's work.' At best, such idle speculations will be the subject of jokes. Such speculation can be a sort of testing on this side of Christ's return, however, if it forces us to confront these less-sturdy parts of our beliefs.
(incidentally, if Gen 6:1-2 is a particular issue, you might consider this sidebar)