Brass and iron as in Isaiah 48:4 and Daniel 7:19 signify what is hard.

In Genesis 4:22, brass signifies natural good. (Arcana Coelestia 421)

In Numbers 21:9, this signifies the Lord's divine natural. (Apocalypse Revealed 49)

Brass also signifies the good in man's natural and the sensuous in the Lord. (Arcana Coelestia 197, Apocalypse Revealed 49, Apocalypse Explained 705)

(参考: Apocalypse Explained 70)

697. And to destroy them that are destroying the earth, signifies hell to those who destroy the church. This is evident from the signification of "to destroy," as being, in reference to those that destroy the church, damnation and hell; for as "to give the reward to His servants, the prophets and the saints," signifies salvation and heaven to those who are in truths from good, that is, who constitute the church, so "to destroy" the earth signifies damnation and hell. Also from the signification of the "earth," as meaning the church (of which above, n. 29, 304, 413, 417); therefore "to destroy the earth" signifies to destroy the church. That in the Word the "earth" means the church has been shown frequently above, also in the Arcana Coelestia. There are many reasons why in the Word the "earth" signifies the church; that is, when no land in particular is mentioned, as the land of Egypt, of Edom, of Moab, of Assyria, of Chaldea, of Babylon, and others, the "earth" (or land) means the land of Canaan, and that land, to those who are in spiritual thought, does not suggest the idea of a land which is earthly, not heavenly, but the idea of the quality of the nation there in respect to the church. So again, when the church, or religion, or worship, is in one's thought, and from this lands are mentioned, the land is not thought of, but the quality of the nation of the land in respect to the church, religion, or worship. For this reason when a man in reading the Word mentions a land, the angels, who are spiritual, think of the church; and what the angels think is the spiritual sense of the Word; for the spiritual sense of the Word is for the angels, and also for those men who are spiritual. For the Word in the letter is natural, and yet inwardly or in its bosom it is spiritual; and whenever the natural is withdrawn the spiritual that is within or in its bosom is disclosed.

[2] Moreover, there are lands in the spiritual world, that is, in the world where spirits and angels are, equally as in the natural world where men are, and these lands are altogether alike in external appearance; there are there plains, valleys, mountains, hills, and there are rivers, and seas, and also fields, meadows, forests, gardens, and paradises; and those lands are in appearance beautiful in exact accord with the state of the church with those who dwell upon them, and they undergo changes in accord with the changes of the church with the inhabitants; in a word, there is a full correspondence of the lands there with the reception of the good of love and the truth of faith with those who dwell there. It is for this reason also that "land" in the Word signifies the church, for in that world according to the quality of the land is the quality of the church there, and correspondence is what makes it be so. In that world the land itself makes one with the church, as a correspondent with its own thing to which it corresponds, just as an effect does with its effecting cause, as the eye with its sight, as speech with its understanding, as action with the will, as the expression of the face with the affection of the thought, in a word, as the instrumental with its principal, of which it is said that they make one thing; so in the spiritual world the quality of the land makes one with that of the church. From this it is clear why in the Word "land (or earth)" signifies the church, and "to destroy the earth" signifies here to destroy the church.

[3] So also in the following passages. In Isaiah:

Is this the man that maketh the earth to tremble, that maketh the kingdoms to quake, that made the world a wilderness, and threw down the cities thereof? Thou hast destroyed thy land, thou hast slain thy people (Isaiah 14:16, 17, 20.)

This is said of Lucifer, by whom Babylon is here meant, as is evident from what here precedes and follows; and "the earth that he maketh to tremble and that he destroyed" signifies the church; the "kingdoms that he maketh to quake" signify the churches into which the general church is divided; the "world that he made a wilderness" signifies the church in general; the "cities that he threw down" signify its truths of doctrine; and the "people that he slew" signify the men of the church whose spiritual life he destroyed.

[4] In Jeremiah:

Behold, I am against thee, O destroying mountain, destroying the whole earth (Jeremiah 51:25).

This, too, is said of Babylon, which is called a destroying mountain, because a "mountain" signifies the love of ruling, here over heaven and earth, which the goods and truths of the church are made to serve as means; therefore "to destroy the whole earth" signifies to destroy the church.

[5] In Daniel:

The fourth beast coming up out of the sea shall devour the whole earth, and shall tread it down and break it in pieces (Daniel 7:23).

This beast, too, signifies the love of ruling over the whole heaven and the whole earth, which love those have who are of Babylon (See above, n. 316, 556); therefore "to devour," "to tread down," and "to break in pieces the earth," signifies to destroy the church utterly. Who does not see that no beast is to come up out of the sea and devour and tread down and break in pieces the whole earth, but that it is some evil and diabolical love that will do thus to the church? In Moses:

There shall not be anymore a flood to destroy the earth (Genesis 9:11).

Here again "the earth" also signifies the church that was destroyed by the antediluvians, but was not again to be destroyed.

[6] In Isaiah:

Jehovah maketh the earth void and maketh it empty, and He shall overturn the faces thereof. In emptying the earth shall be emptied, and in spoiling it shall be spoiled; the habitable earth shall mourn, shall be confounded; the world shall languish, shall be confounded; the earth itself shall be profaned because they have transgressed the laws, overstepped the statute, made void the covenant of eternity, therefore a malediction shall devour the earth. The floodgates from on high are opened, and the foundations of the earth quake; in breaking the earth is broken, in moving the earth is moved, in staggering the earth shall stagger as a drunkard, and it shall be moved to and fro as a balance (Isaiah 24:1, 3-6, 18-20).

Anyone can see that "the earth" here does not mean the earth, but the church. This is said of the church, because the earths (or lands) in the spiritual world, upon which angels and spirits dwell, undergo such changes as are here described according to the changes of state of the church with those who dwell there; they are even moved accordingly. It is said that "Jehovah maketh the earth void and maketh it empty," also that "in emptying it shall be emptied, and in spoiling it shall be spoiled," because the lands there, when the church is laid waste with those who dwell upon them, altogether change their appearance; the paradises, flower gardens, lawns, and the like, with which they before flourished disappear, and things that are unpleasant, such as sandy and rocky places, and plains full of brambles and briars, and like things corresponding to the falsities and evils that have devastated the church, spring up in their place. The devastation of the church in respect to the good of love and charity is signified by "making the earth void," and its desolation in respect to the truths of doctrine and faith is signified by "making it empty and spoiling it," and the change itself by "overturning its faces." "The habitable earth shall mourn, shall be confounded, the world shall languish, shall be confounded, a malediction shall devour the earth," signifies that nothing shall there grow and flourish, but that it shall become barren and filled with useless things, on account of which the earth is said "to mourn, to languish, and to be devoured with a malediction." Because this takes place when those that dwell there have no longer any regard for the holy things of the church, it is said, "because they have transgressed the laws, overstepped the statute, made void the covenant of eternity." Because there the lands are sometimes overflowed, sometimes shaken, and also here and there gape and open towards the hell that lies below and that lifts itself up, and this takes place according to the quality and quantity of the falsities and evils that are loved, and the consequent falsification and denial of the goods and truths of the church, therefore it is said that "the floodgates from on high shall be opened, the foundations of the earth shall quake, the earth shall be broken, and shall stagger like a drunkard," and these things actually take place in the spiritual world, when the state of the church there is changed into a contrary state. From this it can be seen why "the earth" here and elsewhere in the Word, means the church.