Augustine of Hippo, On Nature and Grace Chapter 4: Free Grace

This grace, however, of Christ, without which neither infants nor adults can be saved, is not rendered for any merits, but is given gratis, on account of which it is also called grace. “Being justified,” says the apostle, “freely through His blood.” Whence they, who are not liberated through grace, either because they are not yet able to hear, or because they are unwilling to obey; or again because they did not receive, at the time when they were unable on account of youth to hear, that bath of regeneration, which they might have received and through which they might have been saved, are indeed justly condemned; because they are not without sin, either that which they have derived from their birth, or that which they have added from their own misconduct. “For all have sinned”—whether in Adam or in themselves—“and come short of the glory of God.”