a brick: a block of clay pressed into a mold and hardened in the sun or fired in a kiln
Brick was the ordinary building material of the great river valleys. Where good stone was scarce, workers dug clay from a riverbank, mixed it with water and chopped straw, pressed it into a wooden frame (מַלְבֵּן), and turned it out to bake hard in the sun. The straw was not filler: it bound the clay together and kept the block from cracking as it dried. A brick made this way is cheap, quick, and everywhere, which is why the same word can name a slave gang's daily output and a common family's house wall.
Firing brick in a kiln was a different matter, and an expensive one. It produced a hard, weatherproof block used for city walls, palace facings, and the outer skins of temple towers, and that is exactly what the builders at Babel specify when they say they will burn their bricks thoroughly. The narrator then explains, for readers who lived among plentiful stone, that brick was serving there in place of stone (אֶבֶן) and tar in place of mortar (חֹמֶר).
One word covers a wide range of things because a brick is a manufactured object, made to a set shape and size. A mold yields a block for a wall, a unit an overseer can count and demand by the thousand, and a smooth flat face wide enough to draw a city on. What the word never names is something found rather than made, and that is the point of most of its appearances: brick stands opposite the rough field stone of a lawful altar and opposite the cut and squared masonry (גָּזִית) that only the wealthy could buy.
Nuances
Whether לִבְנַת in Exodus 24:10 is the construct of לְבֵנָה "brick" (a sapphire brick pavement beneath the divine feet) or an abstract noun from לבן meaning "brightness, clearness" parallel to the following colon.
- majorityIt is the brick noun: the elders see tiled sapphire brickwork under YHWH's feet, a reified image of the blue vault seen from below. The Masoretic vocalization, the LXX (ἔργον πλίνθου σαπφείρου), and the Peshitta cognate all read "brick," and the softenings of Targum Onqelos ("precious stone") and the Vulgate ("sapphire stone") presuppose it.; William H. C. Propp, Exodus 19-40, AYB 2A (Yale, 2006), 295-96, 306; Nahum M. Sarna, Exodus, JPS Torah Commentary, at 24:10; Brevard S. Childs, The Book of Exodus, OTL (Westminster, 1974), 505-7; Cornelis Houtman, Exodus, HCOT (Kok/Peeters); Thomas B. Dozeman, Commentary on Exodus, ECC (Eerdmans, 2009), 566-70
- minorityIt is a noun meaning brightness or clearness, standing in synonymous parallelism with "the very substance of the heavens for clearness" in the second half of the verse.; Saadia Gaon, Tafsīr on Exodus, at 24:10; Abraham Ibn Ezra, Commentary on Exodus, at 24:10
What הַלְּבֵנִים in Isaiah 65:3 denotes: freestanding brick incense altars of Mesopotamian (libittu) type, or the brick and tile paving of a flat roof used as a place of offering.
- majorityBrick incense altars of Mesopotamian type, whose very material (brick rather than Levantine fieldstone) marks the cult as foreign, and which belong with the necromantic and chthonic rites of v. 4.; Joseph Blenkinsopp, Isaiah 56-66, AB 19B (Doubleday, 2003), 275-79; Shalom M. Paul, Isaiah 40-66, ECC (Eerdmans, 2012), 592-98; John Goldingay, Isaiah 56-66, ICC (Bloomsbury, 2014)
- minorityThe brick or tile work of a flat roof, the rooftop setting for illicit incense attested in 2 Kings 23:12, Jeremiah 19:13, and Zephaniah 1:5.; David Kimchi (Radak), Commentary on Isaiah, at 65:3