Tex. Code Crim. Proc. art. 19A.202
The court or a person under the direction of the court shall administer the following oath to the grand jurors when the grand jury is completed: "You solemnly swear that you will diligently inquire into, and true presentment make, of all such matters and things as shall be given you in charge; the State's counsel, your fellows and your own, you shall keep secret, unless required to disclose the same in the course of a judicial proceeding in which the truth or falsity of evidence given in the grand jury room, in a criminal case, shall be under investigation. You shall present no person from envy, hatred or malice; neither shall you leave any person unpresented for love, fear, favor, affection or hope of reward; but you shall present things truly as they come to your knowledge, according to the best of your understanding, so help you God."
Tex. Code Crim. Proc. § 19A.202