Why did Gidgiddoni, the Leader of the Nephite Armies, Hang the Gadianton Robbers leader Zemnarihah, on a tree?
"And there were many thousands who did yield themselves up prisoners unto the Nephites, and the remainder of them were slain. And their leader, Zemnarihah, was taken and hanged upon a tree...yea, even upon the top thereof until he was dead." (3 Nephi 4:27-29) 21-22 A.D.
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Answer:
The Nephite people were obeying the Law of Moses that was given to them as recorded upon the brass plates.
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"Yea, and I also thought that they could not keep the commandments of the Lord according to the law of Moses, save they should have the law. And I also knew that the law was engraven upon the plates of brass." (1 Nephi 4:15-16) 600-592 B.C.
Note: The law that was written upon the brass plates was the same law that was given to the prophet Moses, as follows:
“And if a man have committed a sin worthy of death, and he be to be put to death, and thou hang him on a tree.” (Deuteronomy 21:22)