Is it permissible to retract a waiver of private rights concerning a Mudarabah contract without justification?

If a person forfeits their right willingly, maturely, and consciously, they are not permitted to retract it, based on the jurisprudential maxim: "What is forfeited does not return." Its meaning is that whoever forfeits a right that is permissible to be forfeited, it is indeed forfeited and does not return after its forfeiture.