Does my right to demand rent from my brother fall because I told him in a moment of anger, "I don't want rent"?

The basic principle is that when a person relinquishes their right, that right is forfeited, and it is not permissible to reclaim it thereafter, due to the jurisprudential rule: "That which is relinquished does not return." However, the willingness and voluntary choice of the person relinquishing the right must be taken into consideration, as no one's property is lawful without their willing consent. An example of this is that if something is taken from a person out of embarrassment, without their true consent, the one who takes it does not own it; for it is akin to coercion. The context and common practice must also be observed. If the phrase "I don't want rent" indicates anger and not a genuine intention to waive the right, then the right to demand rent remains. But if one has relinquished their right voluntarily and willingly, then they are not entitled to reclaim it.