Virginia constitution
Article II: franchise and officers
Section 6

The districts delineated in the decennial reapportionment law shall be implemented for the November general election for the United States House of Representatives, Senate, or House of Delegates, respectively, that is held immediately prior to the expiration of the term being served in the year that the reapportionment law is required to be enacted. A member in office at the time that a decennial redistricting law is enacted shall complete his term of office and shall continue to represent the district from which he was elected for the duration of such term of office so long as he does not move his residence from the district from which he was elected. Any vacancy occurring during such term shall be filled from the same district that elected the member whose vacancy is being filled.