How do we reconcile the daughters of the Lamanites being at "a place in Shemlon" (Mosiah 20:1) and being spied upon by the priests of Noah, if the priests of Noah had "fled farther into the wilderness" (Mosiah 19:23)? Either the priests of Noah were not very far away from Shemlon and were constantly observing the Lamanite daughters, or they had made a return trip from a more distant location for the specific reason of taking wives. If the latter was the case, then the priests probably were able to predict where the daughters of the Lamanites would be and when they would be gathering.
Based on research by Robert Smith, John Welch, and Gordon Thomasson, just as the month of February means Valentine's Day (and sometimes Bachelors' Leap Year Day) to many Americans, the fifteenth of Av had significance to the ancient Israelites. On that day in the fifth month of the Israelite calendar (which fell originally on midsummer's day), the maidens of Israel would gather to dance. This was, among other things, a "matrimonial holiday for youth."
The ancient holiday is described by Abraham P. Bloch. Bloch concludes that this unnamed holiday was of very early origin, dating back to Moses according to one rabbi. In those days, the festival was primarily a matrimonial holiday, very much like the Jewish Lag Ba'Omer of springtime. Following the conclusion of their summer chores in the fields, youths would turn their attention to "bride-hunting," and the dance of the maidens was "designed to meet that end." The dancing took place outside a temple city--during the period of the Judges, the dances were in the fields outside Shiloh. During later times they were at Jerusalem.
After the return of the Jews from their captivity in Babylon, the holiday took on a much different character. It became the festival of wood-gathering and of offerings of wood for the altar of the temple.
Lehi and his people would only have known the earlier traditions of "dancing and bride-hunting," and perhaps this sheds light on the time when the priests of Noah carried off twenty-four Lamanite daughters to be their wives.
Mosiah 20:1 recounts that "there was a place in Shemlon where the daughters of the Lamanites did gather themselves together to sing, and to dance, and to make themselves merry." Apparently the place was a customary one. The place may have been at an outlying shrine or sacred spot. It was not in the wilderness as such, for the priests went from there into the wilderness (see Mosiah 20:5), but neither was it inside a city.
There the priests found the young women, hid themselves and watched, and sprang out of their hiding places, taking the young women into the wilderness (see Mosiah 20:2-5). The Hebrew idiom translated "lying in wait" usually connotes premeditation and planning, implying that the priests may well have known of this place and the custom for young women to be there. Indeed, the young women apparently became the priests' wives willingly enough; at least we find no indication that any of them tried to escape, and all of them later pled with their brothers and fathers not to kill their husbands (see Mosiah 23:33).
This suggests that the Lamanite daughters had gathered to dance in celebration of a vestige of the preexilic Israelite festival of the fifteenth of Av. Is that how the priests of Noah knew where to go and when to be there? Is that why the young women accepted the priests as husbands? After all, they would have been dancing to attract husbands. [Robert F. Smith, John W. Welch, and Gordon C. Thomasson, "Dancing Maidens and the Fifteenth of Av," in Reexploring the Book of Mormon, pp. 139-141]