Cubit

The cubit (Hebrew ammah, literally mother of the arm or forearm) was the most common unit of linear measurement in the ancient Near East, derived from the length of the forearm from the elbow to the tip of the middle finger. The standard Israelite cubit was approximately 18 inches (about 44 cm), though a longer royal or sacred cubit of approximately 20.5 inches is also attested in Egyptian and Babylonian contexts and was likely used in the construction of the temple (Ezekiel 40:5 distinguishes a cubit plus a handbreadth from the ordinary cubit).

The cubit pervades the measurements of the tabernacle (Exodus 25–27), Solomon's temple (1 Kings 6–7), and Ezekiel's visionary temple (Ezekiel 40–48). Noah's ark was 300 cubits long, 50 wide, and 30 high (Genesis 6:15). Goliath's height was six cubits and a span (1 Samuel 17:4). Jesus's use of cubit in Matthew 6:27 — which of you by taking thought can add one cubit unto his stature? — may refer to either height or the span of life, illustrating the futility of anxious effort to extend what God alone controls.