8 We are convinced, Venerable Brethren, that you will diligently take care to see that all these directives of Ours are conscientiously and exactly fulfilled, carefully and constantly reporting to Us concerning this very serious problem. Since We have taken this matter under Our jurisdiction and, after hearing the views of the Bishops, since the decision rests with Us, We hereby command all Catholics of good will to desist from all disputes among themselves concerning this matter. We are confident that with fraternal charity and perfect obedience they will completely and gladly carry out Our command. If any further difficulty arises among them, they should seek its solution in the following manner: Let them first turn to their Bishops for counsel, and then submit the matter to the Apostolic See for its decision. There is one more point to consider, and it was already implied in what has been said. On the one hand, no one could accuse of bad faith and, under such a pretext, bear ill will toward those who, while firmly defending the teachings and rights of the Church, nonetheless for good reasons have joined or wish to join mixed labor associations in those places where, under certain safeguards, ecclesiastical authority has permitted them in view of local conditions. On the other hand, it would likewise be most reprehensible to oppose or attack the purely Catholic associations (this type of association must, on the contrary, be supported and promoted in every possible manner), and to demand that the so-called intercredal associations be introduced and force their establishment on the grounds that all Catholic associations in every diocese ought to be set up along one and the same pattern.
Source: Singulari Quadam (Vatican.va)