al-Qasim ibn Muhammad القاسم بن محمد بن أبي بكر الصديق · The Book of Financial Transactions

"The Messenger of Allah said: "Volume is to be measured according to the system of the people of Al-Madinah, and weight is to be measured according to the system of the peole of Makkah."' (Sahih) This is the wording of Ishaq (one of the narrators).

the Prophet forbade Muhaqalah, Muzahanah, Mukhabarah and selling with an exception unless it is defined.