SUMMARY: The theme treated in this study presents two elements of interest. On one side it aims at researching through the critical instruments of biblical exegesis those lines of historical-theological development of the old-testamentary motive of the «poor» in his relationship with his opposite, the rich; on the other side, the author is concerned with rendering his research actual, making of it a response to the present-day serious problem concerning poverty in the world. As to the first aspect, he performs his research within the ambit of the Psalms, without omitting the other sapiential literature. The research is sustained also by a confrontation with the literature of the ancient Middle East. The motive of the poor, oppressed by the rich and defended by God, follows an evolutionary process, which departs from a social categorization (poverty) in order to become always an eschatological category, nourished also by prophetic preaching: the poor become the just who suffer oppression at the hands of the rich and the impious, but who become assured of God's final victory. It is the conceptual category on the basis of the Magnificat. The second aspect of the study is no more than the deduction of the consequences from the exegetical rearch. An authentic liberation theology* which must have its roots in the word of God ought to know how to find the right balance by avoiding the two extremes: the spiritualisation which renders evanescent the problem of the poor and its «economization».