When the temple was constructed during Solomon’s reign, a “molten [that is, cast or poured] sea” replaced the portable basin of copper used with the earlier tabernacle. (Ex 30:17-21; 1Ki 7:23, 40, 44) Built by Hiram, a Hebrew-Phoenician, it was evidently called a “sea” because of the large quantity of water it could contain. This vessel, also of copper, was “ten cubits [4.5 m; 14.6 ft] from its one brim to its other brim, circular all around; and its height was five cubits [c. 2.2 m; 7.3 ft], and it took a line of thirty cubits [13.4 m; 44 ft] to circle all around it.”​—1Ki 7:23.

Circumference. The circumference of 30 cubits is evidently a round figure, for more precisely it would be 31.4 cubits. In this regard, Christopher Wordsworth quotes a certain Rennie as making this interesting observation: “Up to the time of Archimedes [third century B.C.E.], the circumference of a circle was always measured in straight lines by the radius; and Hiram would naturally describe the sea as thirty cubits round, measuring it, as was then invariably the practice, by its radius, or semi-diameter, of five cubits, which being applied six times round the perimeter, or ‘brim,’ would give the thirty cubits stated. There was evidently no intention in the passage but to give the dimensions of the Sea, in the usual language that every one would understand, measuring the circumference in the way in which all skilled workers, like Hiram, did measure circles at that time. He, of course, must however have known perfectly well, that as the polygonal hexagon thus inscribed by the radius was thirty cubits, the actual curved circumference would be somewhat more.” (Notes on the King James Version, London, 1887) Thus, it appears that the ratio of three to one (that is, the circumference being three times the diameter) was a customary way of stating matters, intended to be understood as only approximate.

Of Copper. The copper sea was decorated with “gourd-shaped ornaments” and had as its base 12 figures of bulls, facing north, south, east, and west in groups of three. The brim of the sea resembled a lily blossom. The thickness of this large vessel was “a handbreadth [7.4 cm; 2.9 in.].” (1Ki 7:24-26) This huge quantity of copper came from the supplies King David had obtained in his conquests in Syria. (1Ch 18:6-8) The casting was done in a clay mold in the region of the Jordan and was indeed a remarkable feat.​—1Ki 7:44-46.

Capacity. The account at 1 Kings 7:26 refers to the sea as ‘containing two thousand bath measures,’ whereas the parallel account at 2 Chronicles 4:5 speaks of it as ‘containing three thousand bath measures.’ Some claim that the difference is the result of a scribal error in the Chronicles account. However, while the Hebrew verb meaning “contain” in each case is the same, there is a measure of latitude allowable in translating it. Thus some translations render 1 Kings 7:26 to read that the vessel “held” or “would contain” 2,000 bath measures, and translate 2 Chronicles 4:5 to read that it “had a capacity of” or “could hold” or “could contain” 3,000 bath measures. (AT, JB, NW) This allows for the understanding that the Kings account sets forth the amount of water customarily stored in the receptacle while the Chronicles  account gives the actual capacity of the vessel if filled to the brim.

There is evidence that the bath measure anciently equaled about 22 L (5.8 gal), so that, if kept at two thirds capacity, the sea would normally hold about 44,000 L (11,620 gal) of water. For it to have had the capacity indicated, it must not have had straight sides, but instead, the sides below the rim, or lip, must have been curved, giving the vessel a bulbous shape. A vessel having such a shape and having the dimensions stated earlier could contain up to 66,000 L (17,430 gal). Josephus, Jewish historian of the first century C.E., describes the sea as “in the shape of a hemisphere.” He also indicates that the sea’s location was between the altar of burnt offering and the temple building, somewhat toward the south.​—Jewish Antiquities, VIII, 79 (iii, 5); VIII, 86 (iii, 6).

In addition to the copper sea there were ten smaller copper basins resting on carts, and these were evidently filled from the copper sea. (1Ki 7:38, 39) Rabbinic tradition is that the sea was equipped with faucets. The ten basins were used for washing certain sacrifices and likely for other cleansing work, but “the sea was for the priests to wash in it.” (2Ch 4:6) Some rabbis have held that the priests completely immersed themselves in the water of the copper sea, while Josephus says it was “for the priests to wash their hands and feet in.” (Jewish Antiquities, VIII, 87 [iii, 6]) Whatever the procedure, the copper sea is associated with priestly cleansing.

In Prophecy. This may provide a key for understanding the references in the book of Revelation to the “glassy sea” seen before the throne of God in the apostle John’s vision. (Re 4:6; 15:2) It was “like crystal,” perhaps having transparent sides (compare Re 21:18, 21) so that the contents could be seen. Those standing by it, persons victorious over “the wild beast” and its “image,” correspond to those “called and chosen and faithful” ones described at Revelation 17:14; 20:4-6. These serve as “priests of God and of the Christ” and as kings with Christ during his Thousand Year Rule. (Compare 1Pe 2:9.) The position of this priestly class next to the “glassy sea” before God’s throne calls to mind the apostle’s reference to the Christian congregation’s being ‘cleansed with the bath of water by means of the word.’ (Eph 5:25-27) Jesus also spoke of the cleansing power of the word of God that he proclaimed. (Joh 15:3) The ‘mingling of fire’ (Re 15:2) with the watery contents of the sea undoubtedly relates to judgments of God, for fire is frequently used in this connection and God himself is described as “a consuming fire” toward those rejecting his divine will.​—Heb 12:25, 29.

The symbolism of the “glassy sea” in John’s vision thus illustrates Paul’s inspired explanation that the earthly tabernacle and temple with their equipment and priestly functions served as patterns of heavenly things. (Compare Heb 8:4, 5; 9:9, 11, 23, 24; 10:1.) As to the significance of the figures of bulls on which the copper sea of Solomon’s temple rested, see BULL.