Is it permissible for children to waive their share of their father's apartment to their mother with the intention of deferring this share until after her death, while retaining their right to claim it later from her estate?

Registering the house in the mother's name as full ownership, and if the mother takes possession of it, the gift is complete. The children have no right to retract what they relinquished after her death, unless they stated that they only intended the benefit of dwelling. The default in their relinquishment is that it is a gift that has been taken possession of, and it is not permissible to retract it, based on the saying of the Prophet, peace and blessings be upon him: "It is not permissible for a man to give a gift or bestow a present and then retract it, except for a father in what he gives his child. And the example of one who gives a gift and then retracts it is like a dog that eats until it is full, then vomits and returns to its vomit." Even if it was a life tenancy (umra), it is not permissible to retract it. If the mother dies, the house becomes the property of her heirs, including the children who relinquished it, based on the saying of the Prophet, peace and blessings be upon him: "Keep your wealth for yourselves and do not spoil it, for whoever grants a life tenancy (umra), it is for the one to whom it was granted, alive and dead, and for his descendants."