44 Against this host of grave errors, and its secret and open advance, Our Predecessor Leo XIII., of happy memory, worked strenuously especially as regards the Bible, both in his words and his acts. But, as we have seen, the Modernists are not easily deterred by such weapons - with an affectation of submission and respect, they proceeded to twist the words of the Pontiff to their own sense, and his acts they described as directed against others than themselves. And the evil has gone on increasing from day to day. We therefore, Venerable Brethren, have determined to adopt at once the most efficacious measures in Our power, and We beg and conjure you to see to it that in this most grave matter nobody will ever be able to say that you have been in the slightest degree wanting in vigilance, zeal or firmness. And what We ask of you and expect of you, We ask and expect also of all other pastors of souls, of all educators and professors of clerics, and in a very special way of the superiors of religious institutions.
Source: Pascendi Dominici Gregis (Vatican.va)