Is it Islamically permissible for children to waive their share of inheritance to their mother while she is still alive, and what is the legitimate formula for preserving rights in this waiver?

The inherited shops and their income are to be divided among the heirs according to the legal Islamic distribution. It is permissible for a mature,成年 son to relinquish his share of the rent to his mother, or his share in the property, so that she may benefit from it as she wishes.

If the intention of the relinquishment is that the share of the two sons from the shops' rent is a gift to the mother, then this is a promise of a gift for rent that has not yet been received, and it can be revoked in the future. However, if the intention is to relinquish the benefit of their share in the property to the mother for the duration of her life, this is what is called 'umra (a lifetime grant).

Scholars have differed regarding 'umra, and the preponderant opinion is that it belongs to the grantee during their lifetime and then passes to their heirs after their death, based on the saying of the Prophet (peace be upon him): "Keep your properties and do not spoil them, for whoever grants a lifetime grant ('umra), it belongs to the one to whom it was granted, alive and dead, and to his offspring." (Narrated by Muslim). The meaning is that 'umra is a valid and binding gift that the grantee owns completely, and it never returns to the granter.

It is advisable to consult a knowledgeable scholar regarding this matter.