Apophthegmata Laconica
Plutarch
Plutarch. Moralia, Vol. III. Babbitt, Frank Cole, translator. Cambridge, MA: Harvard University Press; London: William Heinemann Ltd., 1931 (printing).
When someone inquired why they kept the laws in regard to bravery unwritten, and did not have
them written down and thus give them to the young men to read, Zeuxidamus said, Because the young ought to accustom themselves to deeds of manly valour, a better thing than to apply their mind to writings.