During the time he holds the office of Governor, he shall not hold any other office: civil, military or corporate; nor shall he practice any profession, and receive compensation, reward, fee, or the promise thereof for the same; nor receive any salary, reward or compensation or the promise thereof from any person or corporation, for any service rendered or performed during the time he is Governor, or to be thereafter rendered or performed.
Official text of the Texas Constitution as published by the Texas Legislative Council.