What is the ruling on subscribing to a supplementary pension scheme that relies on deducting a monthly sum from the employee's salary, with the company adding double the deducted amount, and then these sums are invested in a bank deposit with interest, knowing that the scheme offers many benefits and a part of it cannot be rejected? And is estimating the value of the interest and donating it monthly after retirement a way to avoid the suspicion of consuming usury?

It is impermissible to subscribe to a retirement system if the funds are placed in interest-bearing investment accounts, because those managing the system act as agents for the employees. Thus, everyone incurs sin through the usurious deposit, and merely disposing of the interest is insufficient to lift the sin. Usurious dealings result in the sin of usury and prohibited interest, which is ill-gotten gain that must be disposed of. If the institution mixes the deductions from employees' funds with its own money and disposes of it, this falls under the ruling of a loan. In this case, it is impermissible for the institution to give an allowance to the employee on their balance, because gifts related to a loan are prohibited. However, if the institution does not mix these deductions with its own money and does not dispose of it for itself, then there is no harm in the allowance, but subscribing to the system is forbidden because the money is invested in usury.