23 Meanwhile, as Leo's teachings were being widely diffused in the minds of men, with learned investigations leading the way, they have come to be put into practice. In the first place, zealous efforts have been made, with active good will, to lift up that class which on account of the modern expansion of industry had increased to enormous numbers but not yet had obtained its rightful place or rank in human society and was, for that reason, all but neglected and despised - the workers, We mean - to whose improvement, to the great advantage of souls, the diocesan and regular clergy, though burdened with other pastoral duties, have under the leadership of the Bishops devoted themselves. This constant work, undertaken to fill the workers' souls with the Christian spirit, helped much also to make them conscious of their true dignity and render them capable, by placing clearly before them the rights and duties of their class, of legitimately and happily advancing and even of becoming leaders of their fellows.
Source: Quadragesimo Anno (Vatican.va)