“Arise! Sit down.” What seems like a contradiction to us (get up and sit down) makes perfect sense according to biblical custom. Jerusalem had been like a captive, but now it was to be free. It could arise and get up off the ground, but more than that, it was to reign, and so it was to “sit down.” In the biblical culture, rulers sat while others stood. See commentary on Isaiah 14:13, “sit.”
“daughter Zion.” The Hebrew text reads, “daughter of Zion,” but in this context it is an idiom and comparable to a genitive of apposition (“daughter, that is, Zion”).