The first purpose of the voice to the Lamanites was to protect the Lord’s servants (v. 29). We know of no promise given to Nephi and or Lehi, but the Lord will always protect his servants until their mission is completed (see Mosiah 13:3–4; TPJS, 274; 328). The description of the voice (Helaman 5:30) reminds us of the “still small voice” that was heard by Elijah in Horeb, the mount of God.
11 And he said, Go forth, and stand upon the mount before the Lord. And, behold, the Lord passed by, and a great and strong wind rent the mountains, and brake in pieces the rocks before the Lord; but the Lord was not in the wind: and after the wind an earthquake; but the Lord was not in the earthquake:
12 And after the earthquake a fire; but the Lord was not in the fire: and after the fire a still small voice. [1 Kings 19:11–12]
The Prophet Joseph also referred to “the still small voice, which whispereth through and pierceth all things.” [D&C 85:6]
The second time they heard the voice was an announcement of the kingdom being at hand (Helaman 5:32) The reference to the kingdom must have been to the Savior coming to the earth to establish his higher law. The voice was apparently speaking of the Lord’s time since the time period was about 30 B.C. The message of the third time they heard the voice (v. 33) was not disclosed because of its sacred and divine message. Someday we may learn what was said (see 3 Nephi 26:6–12). The fear and the darkness upon the Lamanites (Helaman 5:34) made them a captive audience, which was probably the purpose desired by the hand of the Lord.