Abinadi is prophesying that the descendants of the priests will kill other righteous individuals by fire. The fulfillment of this prophecy is contained in Alma 25. The priests of Noah kidnap and later marry some 24 Lamanite women which they found while in the wilderness (Mosiah 20:3-5). The descendants of these priests became Lamanites and fought in many battles with the Nephites:
’…in the which they were driven and slain.
And among the Lamanites who were slain were almost all the seed of Amulon and his brethren, who were the priests of Noah, and they were slain by the hands of the Nephites;
And the remainder, having fled into the east wilderness, and having usurped the power and authority over the Lamanites, caused that many of the Lamanites should perish by fire because of their belief—
…And he said unto the priests of Noah that their seed should cause many to be put to death, in the like manner as he was, and that they should be scattered abroad and slain, even as a sheep having no shepherd is driven and slain by wild beasts; and now behold, these words were verified, for they were driven by the Lamanites, and they were hunted, and they were smitten.’ (Alma 25:3-5,12)