What is the command received by Elam and Persia (Media)?
Isaiah 21:2 (ESV)
2A stern vision is told to me; the traitor betrays, and the destroyer destroys. Go up, O Elam; lay siege, O Media; all the sighing she has caused I bring to an end.
Elam and Persia were commanded to go up to overthrow Babylon. As instruments in God's hand, they would bring about the downfall of Babylon (the first mention of Babylon by name follows in Isaiah 21:9).
2 A stern vision is told to me; the traitor betrays, and the destroyer destroys. Go up, O Elam; lay siege, O Media; all the sighing she has caused I bring to an end.