Is it permissible for a deceased mother who has three daughters and a son to bequeath a portion of her gold inheritance to her grandchildren from her son?

It is permissible for a person to make a bequest to a non-heir, provided it does not exceed one-third of their estate, based on the Prophet, peace and blessings be upon him, who said: "Indeed, Allah has bestowed upon you, at the time of your death, one-third of your wealth as an increase for you in your deeds." An heir is excluded from a bequest, as the Prophet, peace and blessings be upon him, said: "Indeed, Allah has given every rightful person their due, so there is no bequest for an heir." Accordingly, a mother may bequeath a portion of her estate to her grandchildren, provided it does not exceed one-third. The heirs are obligated to execute the bequest after her death, as long as her grandchildren are not her legal heirs due to the presence of her direct son. However, if her son dies before her, the bequest to her grandchildren is not valid because they would then become heirs, and in that case, the bequest would only proceed with the consent of the other heirs.