What is the ruling on an investment that yields a fluctuating daily return, with profits and capital received after 30 days, along with the repayment of the principal and interest upon maturity?

For investment to be permissible, three conditions must be met:

1. The funds must be invested in permissible activities, not in usury (riba), gambling, or similar things. 2. There must be no guarantee of the principal capital; otherwise, the contract becomes a loan. 3. Each party's share must be defined as a common percentage of the profit (e.g., 6% or 10% of the profits), not of the capital. The contract is invalid if the profit is unknown.