…the Lord blesses the opposite of what the world calls blessed, saying, “Blessed are the poor in spirit, for theirs is the kingdom of the heavens” (Matthew 5:3). In saying “Blessed are the poor”, why did He add “in spirit”? So as to show that He blesses and commends humility of soul. And why did He not say, “Blessed are those whose spirit is poor”, thus indicating the modesty of their manner of thinking, but “Blessed are the poor in spirit”? So as to teach us that poverty of body is also blessed and fosters the kingdom of heaven, but only when it is accomplished in accordance with the soul’s humility, when it is united to it and originates from it. By calling the poor in spirit blessed He wonderfully demonstrated what is the root, as it were, and mainspring of the outward poverty of the saints, namely, their humility of spirit. For from our spirit, once it has embraced the grace of the gospel teaching, flows a wellspring of poverty that ‘waters the whole face of the ground’ (cf. Genesis 2:6), I mean our outward self, transforming us into a paradise of virtues. Such, then, is the poverty that is called blessed by God.
~St Gregory Palamas (Philokalia vol.4, p.303)
Prayerful Life 