Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
This word is used of sediment found in pits or in streets (Isa. 57:20; Jer. 38:6), of dust mixed with spittle (Jn. 9:6), and of potter's clay (Isa. 41:25; Nah. 3:14; Jer. 18:1-6; Rom. 9:21). Clay was used for sealing (Job 38:14; Jer. 32:14). Our Lord's tomb may have been thus sealed (Mt. 27:66). The practice of sealing doors with clay is still common in the East. Clay was also in primitive times used for mortar (Gen. 11:3). The "clay ground" in which the large vessels of the temple were cast (1 Ki. 7:46; 2 Chr. 4:17) was a compact loam fitted for the purpose. The expression literally rendered is, "in the thickness of the ground,", meaning, "in stiff ground" or in clay.