This prophecy, beginning in verse 14, falls during a part of a prophecy of judgment against Assyria. The sinners and hypocrites in Zion can be one of two things. It can certainly apply to the land of Israel—Zion being a part of Jerusalem, the part where the temple was built—and so he is alluding to the fact that there are hypocrites among the people of Israel. It can also in a sense be dual and refer to the church, because I think that you understand that very frequently God symbolizes the church by the name "Zion." There can be, among those who are part of the Church of God, sinners and hypocrites.
Now these people are responding to the harshness of the prophecies that had gone before this time—those that were aimed at Assyria—and they are wondering, who can ever survive this? God then, through the prophet, gives an answer as to who will be able to survive what is coming. So the answer is: "He who walks righteously and speaks uprightly, who despises the gain of oppression, who gestured with his hands refusing bribes, who stopped his ear from hearing of bloodshed and shuts his eyes from seeing evil." If a person does rightly, if he lives righteously, God extends protection to him so that he won't have to go through the terrible times that are coming.
Now where can this be? Where will this protection be? He says at a "fortress of rocks." Now the stronghold of rock is going to be a place where it's going to be necessary for food to be provided, for water to be provided. It is such a wilderness, it is so desolate that something is going to have to be provided and the implication is that it is going to be provided miraculously by God. Because the place is so desolate, so forsaken, such a wilderness that it seemingly will not support life. Certainly it is dry and maybe only gets two or three inches of rain a year. It's not going to grow anything; it is not going to support life.
The comments regarding the scribe: "where is he who weighs, where is he who counts the towers?" are indications of military personnel, army personalities. One translation says the scribe is "the general who comes," the enlisted, and that has to be tied to verse 19 because the people in this place of protection—those who have lived uprightly—are not going to see the army that is going to be coming against Israel.
In other words who's going to survive? Who's going to escape these things? And so the answer comes. Here is whose going to be worthy to escape all of these things.
Psalms 119:172 gives us a definition of what righteousness is, "All my commandments are righteousness." We understand that the righteousness of Christ is what has to be in us. But we also have to understand that we have to make effort on our part to keep the commands of God. What we have here in Isaiah 33 is very similar to what David wrote in Psalms 15. "Who shall dwell in thy holy hill?" David says. The "who" is going to be in Zion, the parallels are there.