The fifth word of judgment. The furnace. In the besieged city the people shall be tried and purged.

And the word of the Lord came unto me,.... The word of prophecy from the Lord, as the Targum:
saying; as follows:

Israel, compared with other nations, had been as the gold and silver compared with baser metals. But they were now as the refuse that is consumed in the furnace, or thrown away when the silver is refined. Sinners, especially backsliding professors, are, in God's account, useless and fit for nothing. When God brings his own people into the furnace, he sits by them as the refiner by his gold, to see that they are not continued there any longer than is fitting and needful. The dross shall be wholly separated, and the good metal purified. Let those who suffer pains, or lingering sickness, and find that their hearts can scarcely bear these light and momentary afflictions, take warning to flee from the wrath to come; for if these trials are not sanctified by the power of the Holy Spirit, to the cleansing their hearts and hands from sin, far worse things will come upon them.

Refining of Israel in the Furnace of Besieged Jerusalem
Ezekiel 22:17. And the word of Jehovah came to me, saying, Ezekiel 22:18. Son of man, the house of Israel has become to me as dross; they are all brass, and tin, and iron, and lead in the furnace; dross of silver have they become. Ezekiel 22:19. Therefore thus saith the Lord Jehovah, Because ye have all become dross, therefore, behold, I gather you together in Jerusalem. Ezekiel 22:20. As men gather together silver, and brass, and iron, and lead, and tin into the furnace, to blow the fire upon it for melting, so will I gather (you) together in my anger and my wrath, and put you in and melt you. Ezekiel 22:21. And I will collect you together, and blow the fire of my wrath upon you, that ye may be melted therein. Ezekiel 22:22. As silver is melted in the furnace, so shall ye be melted therein (viz., in Jerusalem), and shall learn that I Jehovah have poured out my wrath upon you. - This second word of God rests no doubt upon the figure in Ezekiel 22:15, of the uncleanness or dirt of sin; but it is not an exposition of the removal of the dirt, as predicted there. For that was to be effected through the dispersion of Israel among the nations, whereas the word of God, from Ezekiel 22:17 onwards, represents the siege awaiting Jerusalem as a melting process, through which God will separate the silver ore contained in Israel from the baser metals mingled with it. In Ezekiel 22:18 it commences with a description of the existing condition of Israel. It has turned to dross. היוּ is clearly a perfect, and is not to be taken as a prophetical future, as Kliefoth proposes. Such a rendering is not only precluded by the clause 'יען היות in Ezekiel 22:19, cut could only be made to yield an admissible sense by taking the middle clause of the verse, "all of them brass and tin," etc., as a statement of what Israel had become, or as a preterite in opposition to all the rules of Hebrew syntax, inasmuch as this clause merely furnishes an explanation of היוּ־לסוּג. סוּג, which only occurs here, for סיג signifies dross, not smelting-ore (Kliefoth), literally, recedanea, the baser ingredients which are mixed with the silver, and separated from it by smelting. This is the meaning here, where it is directly afterwards interpreted as consisting of brass, tin, iron, and lead, and then still further defined as סגּים כּסף, dross of silver, i.e., brass, tin, iron, and lead, with a mixture of silver. Because Israel had turned into silver-dross of this kind, the Lord would gather it together in Jerusalem, to smelt it there as in a smelting furnace; just as men gather together brass, iron, lead, and tin in a furnace to smelt them, or rather to separate the silver contained thereon. קבצת כּסף, literally, a collection of silver, etc., for "like a collection." The כ simil. is probably omitted for the sake of euphony, to avoid the discord occasioned by prefixing it to קבצת. Ezekiel mentions the silver as well, because there is some silver contained in the brass, iron, etc., or the dross is silver-dross. התּוּך, nomen verbale, from נתך in the Hiphil, smelting; literally, as the smelting of silver takes place in the furnace. The smelting is treated here simply as a figurative representation of punishment, and consequently the result of the smelting, namely, the refining of the silver by the removal of the baser ingredients, is not referred to any further, as in the case in Isaiah 1:22, Isaiah 1:25; Jeremiah 6:27-30; Malachi 3:2-3. This smelting process was experienced by Israel in the last siege of Jerusalem by the Chaldeans.