law: 21. Relinquishment of exproprietary rights.-
  (1) Save as otherwise provided in sub-section (2), an agreement for the relinquishment of exproprietary rights shall be void, whether such agreement was entered into before or after such rights accrued.
  (2) Notwithstanding anything contained in the first proviso to section 57, where the land transferred by mortgage of the kind specified in sub-section (3) of section 20 consists wholly of a specific area of khudkasht of three or more years, the mortgagor may, by simultaneous agreement in writing, waive his exproprietary rights, and in that case the mortgaged land shall, if the mortgagor redeems the mortgage within ten years of the date of the transfer, be restored to him unencumbered with any tenancy rights.