Mosiah 17:20

"And now, when Abinadi had said these words, he fell, having suffered death by fire; yea, having been put to death because he would not deny the commandments of God, having sealed the truth of his words by his death."

Abinadi was protected from death until he finished preaching. When he finished, King Noah condemned Abinadi to death. Abinadi did not fear death, because he did what God wanted him to do. He was not sinful. This martyrdom shows how dedicated Abinadi was to his God. He gave his all to the Lord.