isaiah 21:2 A grievous vision is declared unto me; the treacherous dealer dealeth treacherously, and the spoiler spoileth. Go up, O Elam: besiege, O Media; all the sighing thereof have I made to cease. - Free Bible Online

      2. dealeth treacherously--referring to the military stratagem employed by Cyrus in taking Babylon. It may be translated, "is repaid with treachery"; then the subject of the verb is Babylon. She is repaid in her own coin; Isa 33:1; Hab 2:8, favor this.
      Go up--Isaiah abruptly recites the order which he hears God giving to the Persians, the instruments of His vengeance (Isa 13:3, 17).
      Elam--a province of Persia, the original place of their settlement (Ge 10:22), east of the Euphrates. The name "Persia" was not in use until the captivity; it means a "horseman"; Cyrus first trained the Persians in horsemanship. It is a mark of authenticity that the name is not found before Daniel and Ezekiel [BOCHART].
      thereof--the "sighing" caused by Babylon (Isa 14:7, 8).

JFB.