The Lord then goes on to say: "Blessed are those who hunger and thirst for righteousness, for they shall be filled." This hunger is not for any bodily food, this thirst is not for any earthly drink: it is a longing to be blessed with righteousness, and by penetrating the secret of all mysteries, to be filled with the Lord himself.
Happy is the soul that longs for the food of righteousness and thirsts for this kind of drink; it would not seek such things if it had not already savored their delight. When the soul hears the voice of the Spirit saying to it through the prophet: "Taste and see that the Lord is good," it has already received a portion of God’s goodness, and is on fire with love, the love that gives joy of the utmost purity. It counts as nothing all that belongs to time; it is entirely consumed with desire to eat and drink the food of righteousness. The soul lays hold of the true meaning of the first and great commandment: "You shall love the Lord God with your whole heart, and your whole mind and your whole strength," for to love God is nothing else than to love righteousness.
Finally, just as concern for one’s neighbor is added to love of God, so the virtue of mercy is added to the desire for righteousness, as it is said: "Blessed are the merciful, for God will be merciful to them."
Remember, Christian, the surpassing worth of the wisdom that is yours. Bear in mind the kind of school in which you are to learn your skills, the rewards to which you are called. Mercy itself wishes you to be merciful, righteousness itself wishes you to be righteous, so that the Creator may shine forth in his creature, and the image of God to be reflected in the mirror of the human heart as it imitates his qualities. The faith of those who live their faith is a serene faith. What you long for will be given you; what you love will be yours for ever.
Since it is by giving alms that everything is pure for you, you will also receive that blessing which is promised next by the Lord: "Blessed are the pure of heart, for they shall see God." Dear friends, great is the happiness of those for whom such a reward is prepared. Who are the clean of heart if not those who strive for those virtues we have mentioned above? What mind can conceive, what words can express the great happiness of seeing God? Yet human nature will achieve this when it has been transformed so that it sees the Godhead "no longer in a mirror or obscurely but face to face" - the Godhead that no man has been able to see. In the inexpressible joy of this eternal vision, human nature will possess "what eye has not seen or ear heard, what man’s heart has never conceived."
From a sermon on the beatitudes by Saint Leo the Great, pope
The Liturgy of the Hours, Vol. IV, Office of Readings
23rd Sunday in Ordinary Time