Remarkably, Laman and Lemuel, rather than changing their minds and their ways, do not even seem to hesitate after the angel has departed. Rather than being filled with remorse for the behavior that had earned them this rebuke, filled with awe at the angel’s visitation, or anxious to discuss the message, they immediately construct reasons why the message had to be wrong. Perhaps they were attempting to show the message wrong so that they could deny the messenger. In any case, their response was denial.
Had they ever previously seen an angel? There is no indication that they had, but obviously they had no problem with the appearance per se. Perhaps their lack of wonder was a tacit admission that their father and brother had tapped into the spiritual realm. Perhaps they believed that such events were possible, but not binding. Clearly, they interpreted this experience almost immediately in a way that denied its relevance to them.
Culture: Nibley provides some cultural background on Laban and his garrison:
As to the garrison of fifty, it seems pitifully small for a great city. It would have been just as easy for the author of 1 Nephi to have said “fifty thousand,” and made it really impressive. Yet even the older brothers, though they wish to emphasize Laban’s great power, mention only fifty (3:31), and it is Nephi in answering them who says that the Lord is “mightier than Laban and his fifty,” and adds, “or even than his tens of thousands” (4:1). As a high military commander Laban would have his tens of thousands in the field, but such an array is of no concern to Laman and Lemuel: it is the “fifty” they must look out for, the regular, permanent garrison of Jerusalem. The number fifty suits perfectly with the Amarna picture where the military forces are always so surprisingly small and a garrison of thirty to eighty men is thought adequate even for big cities. It is strikingly vindicated in a letter of Nebuchadnezzar, Lehi’s contemporary, wherein the great king orders: “As to the fifties who were under your command, those gone to the rear, or fugitives return to their ranks.” Commenting on this, Offord says, “In these days it is interesting to note the indication here, that in the Babylonian army a platoon contained fifty men”; also, we might add, that it was called a “fifty,” hence, “Laban and his fifty.”
Text: In the 1981 edition of the Book of Mormon, chapter 3 ends with verse 31, separating this section from chapter 4. While a change of intent and speaker allows this shift, no division occurred in the 1830 edition of the Book of Mormon. The story of the brass plates and Laban is a single narrative.