The Apostle concludes by gathering together the three great virtues upon which the Christian life rests: faith, hope, and charity. Faith believes the promises of God; hope longs for their fulfillment; charity already begins to possess in some measure the very thing hoped for. Thus all three are necessary during this earthly pilgrimage. By faith the soul walks forward through what it cannot yet see; by hope it perseveres amid trials and delays; by charity it is united even now to God, who is Himself Love. (St. John Chrysostom)

Yet among these three, charity is greatest. The Fathers explain that faith and hope belong especially to the condition of the present life. Faith believes what is unseen, and hope waits for what is not yet possessed. But in heaven faith shall pass into sight, and hope into fulfillment. Charity alone will remain unchanged, because the soul shall continue forever in the love of God. Indeed, charity will not merely remain—it will be perfected. Therefore the greatest virtue is the one that belongs most fully to eternity itself. (St. Augustine)

Faith without charity can become cold and lifeless, consisting only in correct belief. Hope without charity may seek eternal happiness chiefly for oneself. But charity orders everything rightly because it loves God above all things and loves others in God. Augustine teaches that all the commandments are fulfilled in charity because every true virtue finds its proper end there. The soul that grows in charity becomes increasingly free from slavery to pride and self-love, and more capable of resting peacefully in God. (St. Augustine)

The Apostle therefore leads the soul upward through the whole chapter toward this final conclusion: charity is the fulfillment and crown of the Christian life. Gifts, knowledge, sacrifices, and even spiritual understanding all find their true value only when animated by love. The saints are not great because of extraordinary powers, but because they were filled with charity. And heaven itself is nothing other than the perfect and everlasting reign of charity in souls wholly united to God. (St. John Chrysostom)

Sources: St. John Chrysostom, Homilies on First Corinthians, Homily 34; St. Augustine, sermons and writings on the theological virtues and charity.