When a prisoner is committed to jail by warrant from a magistrate or court, he shall be placed in jail by the sheriff. It is a violation of duty on the part of any sheriff to permit a defendant so committed to remain out of jail, except that he may, when a defendant is committed for want of bail, or when he arrests in a bailable case, give the person arrested a reasonable time to procure bail; but he shall so guard the accused as to prevent escape.
Tex. Code Crim. Proc. § 2.18