'Blessed are the poor in spirit, for theirs is the kingdom of heaven.
By "the poor in spirit" is meant those who are poor in earthly desires, and desire nothing but God. These are poor in desires, but not without affection, because they live contented even in this life; and, therefore, the Lord does not say, "Theirs will be the kingdom of heaven," but "theirs is," because even in this life they are rich in spiritual blessings which they receive from God; and thus, however poor they are in temporal goods, they live content with their condition.
They are different from the rich in earthly desires, who, in the present life, whatever riches they possess, are always poor, and live discontented; for the good things of this life do not satisfy our thirst, however much they are increased; wherefore, these persons are never contented, never attaining to the acquisition of what they desire.'
St. Alphonsus Maria de Liguori
Poverty is one of the three Evangelical Counsels.