Why is there a monastic precept forbidding monks and nuns to handle money?

Answer:

by: Venerable Nicolas Thanissaro

The word for 'money' in the olden day scriptural language of Buddhism was 'gold and silver'. For monks and nuns to handle gold and silver was thought to be inappropriate because:

it put the monks and nuns at risk of being assaulted by robbers
it might tempt the monks and nuns into worldly ways of thinking whereby they would have to know the prices of things or haggle to get a good price
it undermined the symbiosis between lay community and monastic community whereby the lay people should be the ones to take care of the material needs of monks so that the monks could get on with their real vocation in life i.e. to study the scriptures (ganda-dhura) and meditate (vipassana-dhura)

In those ancient times, money was not widely used. Barter was the main form of trade. However, if a monk or nun needed to purchase something, a lay person would travel with them and dispense the money they needed.

In the present day society, money is much more indespensible, especially for monks travelling alone. Some conservative monks still use the system of travelling with a lay person who acts as the holder of the purse strings. However, in general monks and nuns are more relaxed about this rule, using the Mendaka's permission clause to be able to use money offered to them to buy meals etc. when travelling. Other monks have have become more technologically literate - no longer handling money, but charging expenses to their credit card.