Ge 11:3, "slime had they for morter": chemer. Hot bitumen was used for cement in the walls of Babylon (Herodotus i. 179). At It, now Heets, eight days' journey from Babylon, the bitumen was obtained. Layard says the cement is so tenacious that it is almost impossible to detach one brick from another. Stubble or straw among the Egyptians, as hair or wool among us, was added to mud or moist clay to increase tenacity.
If this were omitted, or if the sand, ashes, and lime in the proportion 1, 2, 3, were insufficiently mixed, there would be "untempered mortar," tapheel Arabic tapal, pipe-clay like, detritus of felspar (Eze 13:10). The absence of the true uniting cement answers to the false prophet's lie, "thus saith Jehovah, when He had not spoken" (Eze 22:28), false assurances of peace to flatter the people into non-submission to Nebuehadnezzar (Eze 21:29; Jer 6:14; 23:16-17). 'aaphaar "dust" also is used for mortar (Le 14:41-42).
This is spoken of as early as Ge 11:3, in reference to building the tower of Babel: they used brick for stone and slime for morter. In other places it seems to have been employed more for plastering the walls, morter not being so much needed when the buildings were of stone. Le 14:42,45. The rigorous labour of the Israelites in Egypt was in preparing morter as well as making bricks. Ex 1:14. Morter was made by treading the clay. Na 3:14. The work of the false prophets who prophesied peace to Jerusalem when God threatened to bring judgement is compared to building a wall and daubing it with untempered morter: God's wind would blow down the wall. Eze 13:10-15. This teaches a needed lesson that all that is built for God must be built with God's materials, otherwise it will not stand: cf. 1Co 3:11-15.