Pope Pius XI
Quadragesimo Anno §32
Quadragesimo Anno: On Reconstruction of the Social Order
32 With respect to the founding of these societies, the Encyclical On the Condition of Workers most fittingly declared that "workers' associations ought to be so constituted and so governed as to furnish the most suitable and most convenient means to attain the object proposed, which consists in this, that the individual members of the association secure, so far as is possible, an increase in the goods of body, of soul, and of property," yet it is clear that "moral and religious perfection ought to be regarded as their principal goal, and that their social organization as such ought above all to be directed completely by this goal." For "when the regulations of associations are founded upon religion, the way is easy toward establishing the mutual relations of the members, so that peaceful living together and prosperity will result."
Source: Quadragesimo Anno (Vatican.va)