Is it permissible for the son of the deceased to sign on behalf of his mother, who is refusing to take her share of the inheritance, claiming that she has rejected the inheritance?

An heir may relinquish their share of an inheritance and donate it to another, as long as they are of sound mind and mature, because they have the right to dispose of their wealth as they please. The heir's consent is not a prerequisite for owning the inheritance; rather, their share enters into their possession by force of law, and they become its owner. So, if a mother wishes to donate her share of her son's inheritance to another of her sons, she is permitted to do so. However, she must act justly among her children if she has other offspring, and it is recommended to have witnesses to the donation. A mother's refusal to take her share is not considered a relinquishment or a donation, because ownership has already entered into her possession by force of law, and it does not exit except through an explicit declaration of donation or relinquishment.