91.503, but it only requires it for a few operations, not "all"...
(b) Each cockpit checklist must contain the following procedures and shall be used by the flight crewmembers when operating the airplane:
(1) Before starting engines.
(2) Before takeoff.
(4) Before landing.
(5) After landing.
(6) Stopping engines.
(c) Each emergency cockpit checklist procedure required by paragraph (b)(7) of this section must contain the following procedures, as appropriate:
(1) Emergency operation of fuel, hydraulic, electrical, and mechanical systems.
(2) Emergency operation of instruments and controls.
(3) Engine inoperative procedures.
(4) Any other procedures necessary for safety.