Alma 25:11

And now Abinadi was the first that suffered death by fire, because of his belief in God: now this is what he meant, that many should suffer death by fire, according as he had suffered.

Abinadi was the first person to die by fire because he believed in God. This is what he meant. Many others would also die by fire, just like he did.

Abinadi was the first person executed by fire for believing in God. That’s what he meant—that many would die by fire just as he did.