What is the ruling on pure Mudarabah (profit-sharing investment)?

Primary text

There is scholarly consensus, as reported by Ibn al-Mundhir, that the working partner (Al-'Amil) can stipulate a known fraction of the profit, such as one-third or one-half, as his share. The working partner is entitled to profit due to his labor, thus permitting any agreed-upon share, small or large, analogous to wages in leasing or a share of the harvest in sharecropping.