Final answer:
In a biblical context, if a man marries his brother's wife, they would die childless as seen in the story of Onan in the Bible where failing to produce offspring for a deceased brother was condemned.
Step-by-step explanation:
If a man marries his brother's wife, according to the biblical context, the punishment referenced in the Bible would be that they would die childless. This aligns with the story of Onan in Genesis 38:8-10, where Onan was condemned by God for spilling his semen on the ground to avoid providing offspring for his brother. Onan's actions were seen as a failure to fulfill his duty to his deceased brother by preserving his lineage, which was a significant aspect of tribal tradition and family duty in ancient times.