In the book of Alma we read of Alma and Amulek preaching to the people of Ammonihah. Alma 14:7 tells the fate of Zeezrom and the other men who believed their words:
And they spit upon him, and cast him out from among them, and also all those who believed in the words which had been spoken by Alma and Amulek; and they cast them out, and sent men to cast stones at them.
We know that these men were not stoned to death as they are cast out of Ammonihah in the next chapter. However the women and children who believed their words are cast into the fire:
And they brought their wives and children together, and whosoever believed or had been taught to believe in the word of God they caused that they should be cast into the fire; and they also brought forth their records which contained the holy scriptures, and cast them into the fire also, that they might be burned and destroyed by fire.
Why the difference between the two groups? Why were the men stoned then cast out whereas the women and children were destroyed by fire?
John Welch explains how women in biblical times did not have the same rights as men:
Under that law, however, the women, children, or property of these banished men were even less protected. The law was primarily concerned with the conduct of men: “If a man murdereth . . . ,” the law read (Alma 34:11; emphasis added). While women and children were highly valued in biblical society, their status was secondary in Israelite law. Women, for example, could not generally serve as witnesses or inherit property equally with their brothers, and their civil rights were in many ways dependant upon the status and situation of their men. Obviously, in Ammonihah the women and children who believed or had been taught to believe in Alma’s doctrines were not given the protections of the law of Mosiah ensuring them the freedom of belief. In what must be seen as another perversion of the intent of the law by the men in Ammonihah, the law as it was applied in that city apparently granted no rights to women and children in this regard. They were taken and, along with the men’s books, were burned (14:8).
Because women in biblical societies had great potential to teach and influence religious beliefs in the home (e.g., the concerns expressed about marrying women outside the tribes of Israel in Exodus 34:16 and Deuteronomy 7:4), perhaps the people of Ammonihah saw total destruction of the women as the most sure method of guaranteeing that the teachings of Alma and Amulek would not be perpetuated in the community. With the men already expelled from the city, perhaps the people were concerned that, should these women marry again, or should they be allowed to remain and to raise their children to believe in the words of Alma and Amulek, they would—like the wives of Solomon—turn away the hearts of the people “after other gods” (1 Kings 11:4) or walk in ways not favored by the Ammonihahites.– John W. Welch – The Trial of Alma and Amulek
Where would Joseph Smith have learned about this?