De Specialibus Legibus (lib. i‑iv)

And when I speak of witnesses, I mean not such persons as are slaves to pride, but such as are devoted to an admiration of goodness free from all error, by whom the truth is honoured. For wisdom itself is the reward of wisdom; and justice, and each of the other virtues, is its own reward. And truth, as being the most beautiful in the whole company, and as being the chief of all the holy virtues, is in much greater degree its own recompense and reward, affording as it does happiness to all who practise it, and blessings of which they cannot be deprived to their children and descendants.