Partnership: Stipulating Who Conducts Transactions in a Partnership
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2159
If in the partnership contract the partners stipulate a condition that both will buy and sell together, or each one of them on their own will conduct transactions (muʿāmalāt), or only one of them will conduct transactions, or a third party will be hired to conduct transactions, then in such cases, they must act according to the contract.
-Ayatullah Sistani, Practical Laws of Islam, Buying and Selling