The highly contrived story of the seven brothers all marrying one widow was specifically concocted by the Sadducees ("who say there is no resurrection", Matt 22:23, Mark 12:18, Luke 20:27, Acts 23:8) in an attempt to show that the resurrection from the dead is inconsistent with the sacred teachings of the Torah. Thus, it was an attempt at entrapment, see V15 & 34.
Thus, their logic would have gone something like this:
- The Torah requires that a widow marries her brother-in-law. This could happen, say, seven times
- IF there is a resurrection, she will have been married to multiple men and thus, after the resurrection will have multiple husbands
- Such is not permitted by the Torah
- Therefore, the doctrine of the resurrection must be wrong
The Latin name for such an argument is "reductio ad absurdum".
Thus, their question was designed to trap Jesus and show that what He was teaching about the resurrection was not consistent with Torah.
APPENDIX - The Four Questions/Riddles of Matt 22
Note that Matt 22 contains a series of question posed by different groups with the sole intention of silencing Jesus by logical entrapment, V15 & 34. Finally Jesus poses a question that silences His attackers.
- V15-22 - Pharisees ask about paying taxes to Caesar
- V23-22 - Sadducees ask about marriage after the resurrection
- V34-40 - Pharisees ask about the greatest commandment
- V41-46 - Jesus asks about the Christ - Whose Son is He?
Unsurprisingly, Jesus' question was the only one that succeeded in silencing the opponets.