Hebrew word · H3564

כּוּר

kur

furnace

A smelting or refining furnace: a hot enclosed oven for melting metal. It is used literally, and as a picture of severe hardship.

Appears 9 times in 9 verses of the Hebrew Old Testament. · Updated November 01, 2026

What it means

1) furnace, forge, smelting furnace or pot

2) (Qal) to bore, pierce, dig, hew

Abridged from Brown, Driver and Briggs, A Hebrew and English Lexicon of the Old Testament (1906), via STEPBible.org (CC BY 4.0).

Range of meaning: A smelting or refining furnace: a hot enclosed oven for melting metal. It is used literally, and as a picture of severe hardship.
Against the English: All major versions say 'furnace'. That is accurate. In English a furnace is mainly for heating; in this verse it is a place for melting and refining metal.
Used elsewhere in the period: Egypt is called 'the iron furnace' (Deuteronomy 4:20; 1 Kings 8:51; Jeremiah 11:4), a picture of harsh oppression. Isaiah 48:10 says 'I have tested you in the furnace of affliction', and Ezekiel 22:18–22 pictures Jerusalem as a furnace where Israel is melted down like dross.

Range of meaning: Kûr is a metalworking furnace or crucible where ore is smelted or metal refined (HALOT, BDB). Barzel is iron. Joined as 'furnace of the iron,' the phrase means an iron-smelting furnace, a furnace used to work iron.
Against the English: 'Iron furnace' (KJV, BSB, WEB, ESV, NASB) is literal, but a modern reader easily pictures a furnace built out of iron, like a cast-iron stove. NIV's 'iron-smelting furnace' gets the picture right.
How it drifted: English 'iron X' usually means 'X made of iron' (iron gate, iron bar). Hebrew joins nouns as 'X of Y,' and here that means 'a furnace for iron.' The literal English invites the wrong picture.
Used elsewhere in the period: The exact phrase occurs three times, each time of Egypt: Deut 4:20, 1 Kgs 8:51 (Solomon's temple prayer) and here. Kûr appears as a refining crucible in Prov 17:3 and 27:21, and as a furnace of judgment and purging in Ezek 22:18–22 and Isa 48:10 ('I have tested you in the furnace of affliction'). Iron Age smelting furnaces (bloomeries) had to reach about 1,100–1,200°C. They were the most intense controlled fire in the ancient world.

Range of meaning: kûr is a furnace or crucible used in metalworking, for smelting ore or refining precious metal: 'the crucible is for silver and the kûr for gold' (Prov 17:3; 27:21). HALOT connects it with Akkadian kūru, 'kiln, furnace'. barzel is iron. Put together, 'furnace of the iron' most likely means a furnace where iron is smelted.
Against the English: 'Iron furnace' (KJV, BSB, WEB) can make a modern reader picture a furnace made of iron, like a cast-iron stove or boiler. Renderings such as 'iron-smelting furnace' make the metalworking picture clear.
How it drifted: Modern 'furnace' mostly means a heating appliance, and many modern furnaces and stoves are made of iron. To an Iron Age listener, a kûr belonged to the smith's workshop.
Used elsewhere in the period: The same phrase comes back in Solomon's prayer (1 Kgs 8:51) and in Jeremiah (Jer 11:4), both times for Egypt. The furnace becomes a picture of judgment and refining in Ezek 22:18–22 (Israel as slag melted down) and Isa 48:10 ('I have tested you in the furnace of affliction'). In Iron Age Israel and its neighbours, iron was smelted in bloomery furnaces, clay furnaces fed by bellows that reached about 1100–1200 °C. That was far hotter than the kilns used for pottery or bread.

Deuteronomy · 1

Deuteronomy 4:20 מִכּ֥וּר from [the] furnace of

Yet the LORD has taken you and brought you out of the iron furnace, out of Egypt, to be the people of His inheritance, as you are today.

Here: A metalworker's furnace or crucible, used for smelting and refining metal (Prov 17:3; Ezek 22:18–22). It is not a household heater.

1 Kings · 1

1 Kings 8:51 כּ֥וּר [the] furnace of

For they are Your people and Your inheritance; You brought them out of Egypt, out of the furnace for iron.

Here: A metalworker's furnace, not a cooking oven. It brings to mind intense, sustained heat and the transformation of raw material.

Proverbs · 2

Proverbs 17:3 וְכ֣וּר and a smelting furnace

A crucible for silver and a furnace for gold, but the LORD is the tester of hearts.

Here: 'And a furnace': the hot oven where metal was melted and refined. Paired with 'crucible', the two words together stand for the whole process of refining by fire.
Proverbs 27:21 וְכ֣וּר and a smelting furnace

A crucible for silver and a furnace for gold, but a man is tested by the praise accorded him.

Isaiah · 1

Isaiah 48:10 בְּכ֥וּר in a furnace of

See, I have refined you, but not as silver; I have tested you in the furnace of affliction.

Here: "In a furnace of": the hot smelting oven or crucible-furnace of metalwork, not a household oven. It is the same word Deuteronomy uses for Egypt, "the iron furnace" (Deut 4:20), so it casts Babylon as a second Egypt.

Jeremiah · 1

Jeremiah 11:4 מִכּ֨וּר from [the] furnace of

which I commanded your forefathers when I brought them out of the land of Egypt, out of the iron furnace, saying, ‘Obey Me, and do everything I command you, and you will be My people, and I will be your God.’

Here: 'From the furnace of.' A kûr is a metalworker's smelting furnace, the hottest fire an Iron Age person knew. It sets Egypt beside Egypt as a second, vivid picture.

Ezekiel · 3

Ezekiel 22:18 כּ֔וּר a furnace

“Son of man, the house of Israel has become dross to Me. All of them are copper, tin, iron, and lead inside the furnace; they are but the dross of silver.

Here: The metalworker's furnace or melting pot. Within the next verses it becomes an image of besieged Jerusalem.
Ezekiel 22:20 כּ֔וּר a furnace

Just as one gathers silver, copper, iron, lead, and tin into the furnace to melt with a fiery blast, so I will gather you in My anger and wrath, leave you there, and melt you.
Ezekiel 22:22 כּ֔וּר a furnace

As silver is melted in a furnace, so you will be melted within the city. Then you will know that I, the LORD, have poured out My wrath upon you.’”

Word data: STEPBible.org (CC BY 4.0), main text only.