Does the gift given by a mother to her son before her death, with the request that it be returned to him after her death, constitute part of the inheritance that requires the consent of the other heirs, bearing in mind the saying of the Prophet, peace and blessings be upon him: "There is no bequest to an heir"?

What you gifted to your mother became her property and enters into her estate. Her statement that the gift returns to you after her death is considered a bequest to an heir, which is not permissible in Islamic law, due to the Prophet's (peace be upon him) saying: "Indeed, Allah has given every rightful person his right, so there is no bequest for an heir." This bequest is not executed except with the approval of all adult heirs; the approval of a non-adult is not considered. If the heirs approve it, it is permissible; otherwise, it is not.