Buying and Selling: Purchasing Commodities by Weight, Measure, or Viewing
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2101
A commodity that is sold by weight or measure in a particular city must be purchased by weight or measure in that city. However, he can purchase the same commodity by viewing it in another city where it is sold by viewing it.
-Ayatullah Sistani, Practical Laws of Islam, Buying and Selling