72 Christians who take an active part in present-day socio-economic development and fight for justice and charity should be convinced that they can make a great contribution to the prosperity of mankind and to the peace of the world. In these activities let them, either as individuals or as members of groups, give a shining example. Having acquired the absolutely necessary skill and experience, they should observe the right order in their earthly activities in faithfulness to Christ and His Gospel. Thus their whole life, both individual and social, will be permeated with the spirit of the beatitudes, notably with a spirit of poverty. Whoever in obedience to Christ seeks first the Kingdom of God, takes therefrom a stronger and purer love for helping all his brethren and for perfecting the work of justice under the inspiration of charity.
Source: Gaudium et Spes (Vatican.va)