According to the Book of Mormon, Aminadab (/əˈmɪn.ə.dæb/) was a Nephite who fell away from the church, and became associated with the Lamanites.
In the Book of Helaman, after Nephi abdicated the Chief Judgment Seat to Cezoram, he and his brother Lehi went to preach to the Lamanites, who imprison them.
Lamanite prisons
One day, angels came and wrapped Nephi and Lehi in fire, while darkness surrounded the people. The guards were confused, and Aminadab told them to repent. The text implies the guard prayed in faith, had his body encircled with fire, and converted. Aminadab's testimony helped to convert three hundred Lamanites who witnessed the events.
References
Aminadab Wikipedia(Text) CC BY-SA