What does Mark 12:22 mean?

The Sadducees are asking Jesus: if a woman has had seven legal marriages, but no children, which of the seven husbands will she be married to in the afterlife (Mark 12:23)? Mosaic law says that each marriage is lawful and just. But a woman can't have more than one husband at a time—a cultural preference not mentioned in the Mosaic law. In the afterlife, presumably, the woman and all seven men would be present. According to the Sadducees' woodenly literal views, this produces a logical fallacy, one which they interpret to mean there can't be an afterlife.

Reductio ad absurdum is a tool of logic in which you follow through on an opponent's belief to demonstrate a ridiculous end. The Sadducees' use of seven husbands has no inherent importance; it's just meant to be an absurdly large number of husbands. The argument is just as valid with two husbands, whether the childless woman is widowed or divorced.

But, for the Sadducees, the question covers a greater concern. Without the resurrection, their only "life" after death is through their descendants. The Sadducees tend to be the aristocracy of Jerusalem as well as the high priests. But all the wealth and authority in the world is useless without someone to pass it on to. Their disbelief of the resurrection leaves them vulnerable to obscurity.

Jesus' answer is that the Sadducees' rigid insistence that there is no afterlife has blinded them to other, greater, spiritual truths. The Jewish Scriptures prove there is an afterlife when God declares to Moses that He is the God of Abraham, Isaac, and Jacob (Exodus 3:6). If He is their God, they must be alive. As for the Sadducees' question, the understanding of marriage must be interpreted through this greater spiritual truth: there is no marriage in heaven (Mark 12:24–27).