Is the manager entitled to retract a written and documented agreement concerning the mechanism for calculating commission, and to differentiate between employees in its disbursement, on the pretext that it is a bonus or because it was not mentioned in the original contract?

If the contract does not stipulate that these commissions are due to the employee as wages, they are considered a promise from the company to the employees. The general rule is that fulfilling a promise is commendable (mustahabb) but not obligatory, unless the one to whom the promise was made incurs harm due to its non-fulfillment.

If the commissions are not linked to an increase in work and effort, the company is not obligated to fulfill them, and it has the freedom to dispose of them as a gift or donation.

However, if the commissions are linked to an increase in work and additional effort in performance, the company must fulfill them, and the employee has the right to demand them, because this resembles an implicit contract.