The Apostle begins by overturning the judgments of men. For men are naturally moved by what is extraordinary: eloquence, knowledge, miracles, sacrifice, and outward works of greatness. Yet Paul gathers together the very things most admired among Christians and declares that without charity they are empty. Speech may astonish the ear, prophecy may enlighten the mind, faith may accomplish wonders, and sacrifice may appear heroic before the world; nevertheless, if charity is absent, none of these things possesses true life before God. (St. John Chrysostom)
This is because charity is not merely one virtue among many, but the soul and form of every virtue. Without it, even good works become hollow, as a body without life. A cymbal may produce sound, yet it does not live; so too a man may speak well about divine things while remaining inwardly barren of love. Augustine teaches that many desire gifts from God while neglecting the very thing for which all gifts are given. For knowledge without charity puffs up the soul, whereas charity unites it to God. (St. Augustine)
The Apostle also strikes at spiritual pride. One may possess true gifts and yet secretly begin to delight more in the gifts than in God Himself. Thus Paul removes every ground of boasting. He does not say such a man is merely imperfect, but “I am nothing.” Not because the gifts are false, but because without charity they fail to sanctify the one who possesses them. God does not measure greatness as men do. Men look at outward brilliance; God looks to the love from which every action proceeds. (St. John Chrysostom)
Even martyrdom itself profits nothing without charity. This is perhaps the most fearful statement of all. For there are those who endure hardship out of pride, stubbornness, or desire for glory. But charity seeks neither praise nor self-exaltation. It desires only God and the good of the other. Therefore the smallest act done with true charity is greater before God than the most astonishing work performed without it. For charity alone endures eternally. Prophecies shall pass away, knowledge shall one day cease, faith shall give way to sight; but charity already participates in the life of heaven itself. (St. Augustine)
Sources: St. John Chrysostom, Homilies on First Corinthians, Homilies 32–33; St. Augustine, sermons and writings on charity, humility, and the theological virtues.