No one dares attempt to lay hands on Abinadi because they witness in him a visible transformation. The power of the spirit in Abinadi was sufficient that it became a visible "luster." We do not read of such a visible expression of the spirit's protection in an incident between Nephi and his brothers, but clearly Nephi warned his brothers just as Abinadi has warned his would be captors. Somehow, Nephi's brother's clearly received the message, just as in this case (see 1 Nephi 17:47-49).
Heavenly beings are frequently described in terms of "light" (see, for instance, Joseph Smith History 1:16; 1:30). It would appear that the things of the spiritual realm may be accompanied by what we perceive as light, and the powerful presence of the spirit with Abinadi (and also Moses) was such that the face appeared transformed and lighted. Since the face is our major means of identification of each other, and becomes symbolic for the whole person at times, it is quite possible that there was an aura of light all around Abinadi, but that it was most evident in the face as that would be where we would naturally concentrate our vision.
Textual: From Daniel Ludlow:
"Notice the following interesting reference concerning Abinadi as he made his defense before Noah and the wicked priests: "the Spirit of the Lord was upon him; and his face shone with exceeding luster, even as Moses' did while in the mount of Sinai, while speaking with the Lord." (Italics added.) This statement is of particular interest because of the controversy among biblical scholars and translators concerning the facial appearance of Moses after he had talked with the Lord on the mount of Sinai. The King James Version renders Exodus 34:30 as follows: "And when Aaron and all the children of Israel saw Moses, behold, the skin of his face shone; and they were afraid to come nigh him." However, the Catholic translators of the Douay Version followed the pattern of the Septuagint Bible by translating the same verse as follows: "And he knew not that his face was horned from the conversation with the Lord. And Aaron and the children of Israel seeing the face of Moses horned, were afraid to come near." Because of this faulty interpretation, the great sculptor Michelangelo put horns on his famous statue of Moses!"(Ludlow, Daniel H. A Companion To Your Study Of The Book Of Mormon. , Deseret Book, 1976, p.182).