74 We are fully aware of the fact that many young people have already responded wholeheartedly to the invitation of Our predecessor Pius XII , summoning the laity to take part in missionary work. (60) We also know that other young people have offered their services to public and private organizations that seek to aid developing nations. We are delighted to learn that in some nations their requirement of military duty can be fulfilled, in part at least, by social service or, simply, service. We commend such undertakings and the men of good will who take part in them. Would that all those who profess to be followers of Christ might heed His plea: "I was hungry and you gave me to eat; I was thirsty and you gave me to drink; I was a stranger and you took me in; naked and you covered me; sick and you visited me; I was in prison and you came to me." (61) No one is permitted to disregard the plight of his brothers living in dire poverty, enmeshed in ignorance and tormented by insecurity. The Christian, moved by this sad state of affairs, should echo the words of Christ: "I have compassion on the crowd." (62)
Source: Populorum Progressio (Vatican.va)