The high wind knows the strength of grass, and the board swings to know the sincerity of ministers. Brave people know justice in peace, but wise people are kind. Explain this poem?

Li Shimin wrote a famous poem "To Xiao Yu's Love": "Strong winds know strong grass, and steady swings know loyal ministers. The brave know righteousness, and the wise will be benevolent. " Only in the strong wind can we see the tenacity of the grass; In times of turmoil, we can see whether a courtier is loyal to the country. How can a brave man know morality? A wise man must have kindness in his heart. This poem highly praised Xiao Yu and fully affirmed his loyalty. At first, Xiao Yu was also an official of the Sui Dynasty, but later he surrendered to Li Shimin and was highly valued and appreciated by Li Shimin. Note: The titles of two articles in The Book of Songs: "Ban Dang" reflect the turbulent situation of the times.