Sociological: It is not insignificant that the rest of King Benjamin’s catalog of his administration should follow the statement that he had not sought riches at the expense of his people. It is very possible that King Benjamin intends verses 12 and 13 to be similarly contrastive to other Kings as are verses 10 and 11. In verses 10 and 11 Benjamin sets himself apart from the Kings who declared themselves divine, and in verses 12 and 13 Benjamin contrasts the nature of his administration as different from that of the “other” Kings – specifically in the common aspects of the “other” kingdoms which he does not suffer in his own realm. Each of the elements listed makes the most sense in his context if the people understand that these things are common expectations in other city/city-states, and that they are unique in their opposition to them.
“The use of dungeons or prisons was apparently tolerated in Israel (see Jeremiah 37:15; 1 Nephi 7:14), generally in the land of Nephi (see Mosiah 17:5), in the land of Ammonihah (see Alma 14:18,23), and among the Lamanites (see Helaman 5:21); by by special dispensation, the use of prisons was not allowed in Zarahemla under King Benjamin or in other lands by special royal decrees (see Alma 23:2) (Welch, John W. ”Benjamin, the Man: His Place in Nephite History." In: King Benjamin’s Speech. FARMS 1998, p. 40).
The decree in Alma 23:2 was a special protection for sons of Mosiah and other missionaries in Lamanite lands. That such a special decree was needed highlights the more common use of the prison or dungeon among the Lamanites. There does not appear to be any significant difference in the usage of “dungeon” or “prison,” since they may be both referenced in the same context in Alma 8:30.
Similar to the special protection of the sons of Mosiah highlighting the more common usage, the message of King Benjamin is that a well known form of punishment has been spared his people through his own decree. The people clearly knew what prisons were, and King Benjamin has reminded them that they have not had to be subject to them. Since we know that Benjamin’s reign was not always peaceful, he had some other way of dealing with lawbreakers – most likely banishment (see Words of Mormon 1:16 on the defections to the Lamanites).
Likewise, the threat of slavery had to be a real option, or Benjamin’s prohibition of it would be nothing to brag about. Mesoamerica practiced slavery, with firm attestation among both the Maya and the Aztec. For Maya slavery (geographically closer to Zarahemla, though the best sources are much later in time) slavery may have been practiced in both the Classic and Postclassic depending on how certain iconography is read (Morley, Sylvanus. The Ancient Maya. Stanford University Press, 1956, p. 159). We should be careful, however, about reading too much of US history with slavery into ancient Mesoamerican practice; “the term is evocative, and it may well be that Maya slavery was less exploitative, and more like the villeinage of medieval England, or the patron-client relationship with mutual obligations that Tambiah notes for medieval Southeast Asia” (Hammond, Norman. “Inside the Black Box: Defining Maya Polity.” In: Classic Maya Political History. School of American Research and Advanced Seminar Series. 1996, p. 265). In any case, slavery was clearly seen as distasteful, and ascribed to King Benjamin’s credit that it was avoidable in the land of Zarahemla.
The prohibitions against murder and stealing may be nothing more than the standard social laws. However, since most societies will prohibit murder and stealing, it may also be that Benjamin is making a specific contrast to something else. While I cannot offer a reference for stealing, it is possible that the prohibition against murder may have come as a reaction against Mesoamerican human sacrifice, a practice which often accompanied the nature of Mesoamerican slavery (Morley, 1956, p. 159; Duran, Fray Diego. Book of the Gods and Rites of the Ancient Calendar. University of Oklahoma Press, 1971, pp. 138, 175, 204). Assuming the context of Benjamin setting himself apart from the other Kings, this becomes a plausible scenario.
Plunder and adultery may also have somewhat different connotations in a Mesoamerican setting. Plunder comes from the spoils of conquest over another people. While the people of Benjamin have been subject to wars which would have resulted in the plunder of Zarahemla, Benjamin is apparently not only forbidding the plunder, but the initiation of the war out of which the plunder would have been a nearly natural consequence. The case of adultery may send us back to Jacob’s issues with multiple wives. Benjamin would appear to have continued the “one man, one woman” rule, which would certainly contrast with neighboring cultures.
As a summation, Benjamin notes that he has not suffered that they should “should commit any manner of wickedness.” While unstated, this is still in the line of contrasting their society with other neighbors who do commit all “manner of wickedness.” In the tradition of ancient societies, the self definition of King Benjamin’s people included their understanding that they are different from the “others,” a practice that we have seen as early as Enos (who was probably so taught by his father).
Textual: A possible confirmation that these specific legal prohibitions began as a contrast to Lamanite (in the wide sense) society is found in the proclamation of the king of the Lamanites after his conversion by the sons of Mosiah II “Alma 23:3 …that they ought not to murder, nor to plunder, nor to steal, nor to commit adultery, nor to commit any manner of wickedness). The very ordered repetition here and the presence of the sons of Mosiah suggests that this legal list became a code for Nephite law (Welch, John W. ”A Masterful Oration.“ In” King Benjamin’s Speech. FARMS 1998, p. 61 notes the repetition of the phrases and suggests that it is due to the importance given this text in future years). The repetition of the same (or nearly the same) legal list in Mosiah 29:36, Alma 30:10, and Helaman 6:23 indicates both that the language of Benjamin’s speech became normative for his people, but that these principles became a legal code for the Nephites (see especially Alma 30:10).
It is also important to note that the usage in Mosiah 29:36 follows in the context once again of the iniquity of unnamed kings:
Mosiah 29:31
For behold I say unto you, the sins of many people have been caused by the iniquities of their kings; therefore their iniquities are answered upon the heads of their kings…35 And he also unfolded unto them all the disadvantages they labored under, by having an unrighteous king to rule over them;
36 Yea, all his iniquities and abominations, and all the wars, and contentions, and bloodshed, and the stealing, and the plundering, and the committing of whoredoms, and all manner of iniquities which cannot be enumerated—telling them that these things ought not to be, that they were expressly repugnant to the commandments of God.