First, the Old Testament shows that whenever professing believers become so dominant in a society that they can influence its structures, they are responsible to help establish justice. John Howard Yoder is correct in stating that the messianic King is never presented in Scripture as the ruler over a realm of shadows, a never-never land outside history. He is the Son of David who is to bring in the Year of Jubilee (the redistribution of wealth so that the poor recover their possessions), who is finally going to establish justice for the poor and who is going to liberate the oppressed by casting down their oppressors and raising up the humble to leadership.
In the New Testament, Jesus comes bringing not only forgiveness to the faithful but healing for the sick, bread for the hungry, sight for the blind and hearing for the deaf. We might be inclined to spiritualize all these matters, but we have seen Christians within history bringing them to literal fulfillment! We would do better to broaden their meaning to include the healing of sick societies.
The Christians in Acts practices "Pentecostal economics," not by abolishing private property but by putting all their goods at the disposal of one another and the kingdom. Paul engineered redistribution of wealth among the churches. If we had only Matthew 25:31-36 and the letter of James, we would have to conclude that the New Testament is as uncompromisingly earthy and literal as the Old in its demands for social justice. It calls for sacrifices which are not payable only in spiritual and emotional currency. They cost money and effort as well as love.
We see then that Christians are responsible to carry out a holistic ministry which cares for people's bodies as well as their souls and which seeks to change structures as well as hearts. . . . it is never the case that we have a first priority to see a man's soul saved, and then, if our funds hold out, to do something for him socially and materially. Our responsibility is to respond to him in love on every level, within the bounds of what is possible and practicable.
Dynamics, pp. 387-89