“…they durst not open their mouths.” What other more human reaction could their have been to this spectacular event. These people had been speaking, now they were silent. They had been speaking about the Messiah, and here he was in their midst. Their world had changed in this short period of time. They were conversing, now they are quiet.
Nephi heightens the drama of the situation by noting that even with the annunciation of the Son of God by the Father himself, there were those who did not yet understand that it really was the Son. It might have been an angel representing the Son.
Vocabulary: The word “wist” is an obsolete verb form in English. It is undoubtedly used in this text in imitation of KJV speech patterns, although it does appear in the 1828 edition of Webster’s Dictionary (An American Dictionary of the English Language, Noah Webster, 1828, electronic edition, © 1998 Deseret Book Company.) The meaning is to “to be or become aware (of); learn; know.” The present form of the verb was “wit.” (Funk & Wagnalls Standard Dictionary. Britannica World Language Edition. New York, 1959).
Cultural: Christ descends dressed in white. When the modern reader sees this passage we immediately understand that the clothing is symbolic of the purity of the risen Lord. There would have been a different cultural assumption for a people who lived in Mesoamerica. As in Asia, the Mesoamerican association of white was with death. Thus one descending in white would be declaring that this was one who was, or had, died. This is an important part of the message, however. See the comment following verse 14.