Casti Connubii §3

³ Yet not only do We, looking with paternal eye on the universal world from this Apostolic See as from a watch-tower, but you, also, Venerable Brethren, see, and seeing deeply grieve with Us that a great number of men, forgetful of that divine work of redemption, either entirely ignore or shamelessly deny the great sanctity of Christian wedlock, or relying on the false principles of a new and utterly perverse morality, too often trample it under foot. And since these most pernicious errors and depraved morals have begun to spread even amongst the faithful and are gradually gaining ground, in Our office as Christ's Vicar upon earth and Supreme Shepherd and Teacher We consider it Our duty to raise Our voice to keep the flock committed to Our care from poisoned pastures and, as far as in Us lies, to preserve it from harm.