Is what the questioner did, regarding the drafting of a debt acknowledgment for her sister, to whom she transferred her house, stating that her sister has the right to claim the house after the questioner's death, with her mother remaining in it until her death, permissible according to Sharia, especially since the law in her country does not validate the condition of a life estate ('Umra)? And if it is not permissible, what is the legitimate Sharia solution to return the house to her?

The saying that lifetime gifts ('Umra) and conditional gifts (Ruqba) are immediate transfers of ownership, not deferred or suspended until death, means that the donor (al-mu'mir) promptly bestows the usufruct to the donee (al-mu'mar) immediately, without deferring its ownership transfer. If the questioner wishes the house to return to her sister after her death, then transferring its ownership to her after her death is considered a will. A will to an heir is not permissible, nor is it permissible for more than one-third (of the estate). Therefore, it would have been more appropriate for her sister to grant her the usufruct of the house for her lifetime without transferring ownership of the property itself. Thus, upon her death, the house would return to her sister.