Importance of Zira in Islam

Many laws in islam have lengths measured in zira. Some examples are:

(1) Distance between wells must be atleast 40 zira.

(2) If some nijasat (excretions, alcohol, blood) falls in a pool/pond etc of water and neither of color, smell, taste of water change then water still becomes nijasat, unless the size of pool/pond etc is 10 zira x 10 zira or 20 zira x 5 zira.

Zira is also used in some arabic units of measurement, such as

(1) Mil. 1 mil = 4000 zira. Note that the term "mile" in english is derived from arabic "mil". One mile = 1600 meters, One mil = 4000 zira = 2000 meters.

(2) 1 farsukh = 3 mils = 12,000 zira.