The so-called "Fu De" is actually a format of ancient examinations. According to the examination rules, any designated and limited poem title must be preceded by the word "Fu De". It can be seen that the examination rules have been rigid since ancient times.
So this poem is actually a proposition composition written by Bai Juyi during the exam, and the limited topic is "Ancient Original Grass". And "Farewell" is Bai Juyi's own subtitle.
For all designated test questions, the word "Fu De" must be added before the question. The method is similar to chanting things. "Farewell with Ancient Wild Grasses" expresses the feeling of farewell to friends through the description of the wild grasses on the ancient plains.
Bai Juyi always advocated that poetry should be easy to understand, but he was not opposed to the use of metaphors. The title of the poem "Ancient Yuancao" has the word "farewell", which is obviously a poem to send off a friend. Almost the whole article is written in grass, which is actually a metaphor, using the lush vegetation to show the lingering friendship between friends when they part ways. The love is profound and the metaphor is particularly clever. It is worthy of being Bai Juyi's famous work.
Extended information:
Original text and translation of "Farewell to the Ancient Grassland":
Original text: When the grass grows in the original land, it will flourish every year. Wildfires never burn out, but spring breezes blow them again. The distant fragrance invades the ancient road, and the clear green meets the deserted city. I also sent the king and grandson away, full of love.
Translation: The wilderness is covered with lush green grass. Every year in autumn and winter, the grass turns yellow and becomes thicker in spring. Wildfires cannot burn away the weeds all over the ground, and the spring breeze blows the earth green again. The fragrant weeds in the distance cover the ancient road, and the sun shines green even on the deserted city. Today I came to bid farewell to an old friend again, and even the lush grass was full of farewell.