(Isa. 13:2; refer in this text to 2 Ne. 15:26–30 & 2 Ne. 21:12)
The word “banner” is translated from the same Hebrew word as is translated “ensign.” In Isaiah 5:26 … The banner is therefore the Book of Mormon. The high mountain upon which the book is to be lifted is the Americas… .
Those who lifted up the banner were to exalt the voice and wave the hand or give a signal to go into the gates of the nobles (see footnote in the Book of Mormon under 2 Nephi 23:2). The nobles at the time of the coming forth of the Book of Mormon were the Gentiles, the ones who were living in the Americas upon the land promised to Joseph (Morm. 5:19–20).
(Monte S. Nyman, Isaiah: Prophecies of the Restoration [Salt Lake City: Millennial Press, Inc., 1998], 32–33.)
The gates of Eastern cities were an important part of ancient city life. They were not only places of entrance and exit, but also served as places of private and public business transactions. The gates were often taken as representing the city itself… . In the Isaiah context, the meaning is probably an invitation for those who are fleeing Babylon to enter the holy cities of Jerusalem and Zion (the new Jerusalem). (See D&C 133:12–14.)
(Hoyt W. Brewster, Jr., Isaiah Plain and Simple [Salt Lake City: Deseret Book Co., 1995], 125–26.)
The “battle flag” could be used to rally the forces of the world against Jerusalem (see Isa. 10), or it might serve as an “ensign” … around which the Lord’s servants and saints gather against the evil forces of the world. (See Isa. 11:10; 62:10, where the same word is used.) In either case, it will assemble a mighty force that will fulfill some of the Lord’s judgments against the wicked.
(Victor L. Ludlow, Isaiah:Prophet, Seer, and Poet [Salt Lake City: Deseret Book Co., 1982], 183.)
This verse is addressed to Cyrus and the hosts of Medes and Persians whom Cyrus would assemble in the highlands east of the Tigris River. They were to raise up the banner and descend on the nobles of Babylon. It is interesting that in the Joseph Smith Translation it says “MY banner,” suggesting that Cyrus is representing the rod of God’s wrath as he goes forth to conquer Babylon… .
In the latter days the Lord’s banner is raised up, but for a different purpose. It is to lead God’s people out of Babylon or the wickedness of the world.
(W. Cleon Skousen, Isaiah Speaks to Modern Times [Salt Lake City: Ensign Publishing Co., 1984], 260–61.)
Because city gates were public passageways, they took on the nature of a “public square” where legal and civil events occurred… . Immediately inside many city gates was an area where officials met and deliberated. To “sit in the gate” (or its variant “sit in the seat”) implied one’s prominence in the community… . Even kings sometimes positioned themselves “in the gate” (2 Sam. 18:24; 19:8)… .
The pattern was established even before the Israelites settled in cities, with Moses judging the people “in the gate of the camp” during their wilderness wanderings (Ex. 32:26)… .
Because so much commercial and civil business was transacted at the city gate, it became a prime image for prophetic denunciations of a corrupt society… . While the majority of biblical references are to literal gates, they also assume figurative qualities. Sometimes they are a synecdoche for an entire city: “Her gates shall lament and mourn; ravaged, she shall sit upon the ground” (Isa. 3:26 NRSV); ”‘Wail, O gate; cry, O city” (Isa. 14:31 NRSV).
(Dictionary of Biblical Imagery, ed. Leland Ryken, James C. Wilhoit, and Tremper Longman III [Downers Grove, Illinois: InterVarsity Press, 1998], 321–22.)