The standard for measures of length among the Hebrews. They derived it from the Babylonians, but a similar measure was used in Egypt with which they must have been familiar. The length of the cubit is variously estimated, since there seems to have been a double standard in both countries, and because we have no undisputed example of the cubit remaining to the present time. The original cubit was the length of the forearm, from the elbow to the end of the middle finger, as is implied from the derivation of the word in Hebrew and in Latin (cubitum). It seems to be referred to also in De 3:11: "after the cubit of a man." But this was too indefinite for a scientific standard, and the Babylonians early adopted a more accurate method of measurement which passed to the nations of the West. They had a double standard, the so-called royal cubit and the ordinary one. From the remains of buildings in Assyria and Babylonia, the former is made out to be about 20,6 inches, and a cubit of similar length was used in Egypt and must have been known to the Hebrews. This was probably the cubit mentioned by Eze 40:5 and perhaps that of Solomon’s temple, "cubits after the first measure" (2Ch 3:3), i.e. the ancient cubit. The ordinary cubit of commerce was shorter, and has been variously estimated at between 16 and 18 or more inches, but the evidence of the Siloam inscription and of the tombs in Palestine seems to indicate 17,6 inches as the average length. See Weights and Measures. This was the cubit of six palms, while the longer one was of seven (Eze 40:5). The cubit mentioned in Jud 3:16 is from a different word in Hebrew (gomedh) and was probably shorter, for Ehud girded it on his thigh under his clothing.
The New Testament references are Mt 6:27; Lu 12:25, "Which of you .... can add a cubit unto the measure of his life?"; Joh 21:18, "about two hundred cubits off"; Re 21:17, "the wall thereof, a hundred and forty and four cubits."