This shaking of hands is not a friendly gesture. It refers to giving the enemy a signal prior to attacking them. It signifies that in the last days the Lord will give the wicked a signal, or sign, before his armies attack. But we should note the great mercies of the Lord. He would first raise an ensign to the nations, the restored church, to teach them the new and everlasting covenant; he would lift a banner upon the high mountain by building temples all over the earth; and he would exalt the warning voice through his prophets and servants. Having rejected all these overtures, the wicked would be given a sign—the last of many—the Lord would shake the hand before the enemy. It means their destruction is imminent. The wicked may run to the houses of the nobles seeking protection, but they will receive none, for it is the Lord’s nobles and sanctifies ones who will triumph.
“Jehovah’s sanctified ones (Josh. 3:5) are those who are temple worthy, who actually attend the temple, and who are made holy by Christ’s power. In ancient Israel the soldiers prepared for the holy war by participating in holy rituals connected with the temple (Deut. 23:10-15). In this dispensation, Jesus Christ’s soldiers (members of the Church) prepare for the battle against Babylon by participating in temple rituals.” (Donald W. Parry, Jay A. Parry, and Tina M. Peterson, Understanding Isaiah, 131 as taken from Commentaries on Isaiah in the Book of Mormon, ed. by K. Douglas Bassett, [American Fork, UT: Covenant Publishing Co., 2003], 200)