There are two instances in the Book of Mormon of “outstretched hands” are a sign of exerting supernatural power:
1 Nephi 17:53-54:
And it came to pass that the Lord said unto me: Stretch forth thine hand again unto thy brethren, and they shall not wither before thee, but I will shock them, saith the Lord, and this will I do, that they may know that I am the Lord their God.
And it came to pass that I stretched forth my hand unto my brethren, and they did not wither before me; but the Lord did shake them, even according to the word which he had spoken.
And when Amulek saw the pains of the women and children who were consuming in the fire, he also was pained; and he said unto Alma: How can we witness this awful scene? Therefore let us stretch forth our hands, and exercise the power of God which is in us, and save them from the flames.
But Alma said unto him: The Spirit constraineth me that I must not stretch forth mine hand; for behold the Lord receiveth them up unto himself, in glory; and he doth suffer that they may do this thing, or that the people may do this thing unto them, according to the hardness of their hearts, that the judgments which he shall exercise upon them in his wrath may be just; and the blood of the innocent shall stand as a witness against them, yea, and cry mightily against them at the last day.
In these scriptures, no speech is involved, which is contrary to the other Book of Mormon uses of “stretching forth hands” accompanied by speech. It is interesting that of the forty-three biblical instances in which the idiom nāṭâ yād “extend the hand” is used to exert a supernatural power, none of them include a curse or speech.
Wouldn’t it have been easy for Joseph to have mentioned a curse or speech when stretching forth hands to exert supernatural power? How did he know they should remain silent?