On February 20, 1866, the constitutional convention referred a number of proposed revisions to various committees, including proposals concerning bail, the removal of officers appointed by the Governor, the election of justices of the Supreme Court, and the article on slavery.
The committee on the Legislative Department reported its recommendation relating to a proposal to delete a provision that appeared in both the 1845 and 1861 Constitutions, which prohibited religious ministers from serving in the legislature. That proposal ultimately was rejected, and in Article III, section 26, the 1866 Constitution provided:
Ministers of the gospel being by their profession dedicated to God and the care of souls, ought not to be diverted from the great duties of their functions; therefore, no minister of the gospel, or priest of any denomination whatever, shall be eligible to the Legislature.
Update: Thanks to Texas Bar Today for naming this one of the top blogs of the week!