From
唐太宗《
赐萧瑀》(Emperor Tang Taizong, early Tang, ~630s), a five-character quatrain praising his loyal minister Xiao Yu:
疾风知劲草,
板荡识诚臣。
勇夫安识义,
智者必怀仁 (A fierce wind reveals the strong grass; turmoil reveals the honest minister. How could the merely brave know duty? — only the wise always hold benevolence).
板荡 = two 《
诗经·
大雅》poems,
板 and
荡, both mourning a chaotic age; the word came to stand for political upheaval itself.