It comes from two allusions: a skilled worker and shining on you.
Experts who know cows: refers to those who have mastered the objective laws of things after repeated practice, and are handy in doing things and using them freely.
Shine on you: green is extracted from blue grass, but the color is darker than blue. Metaphor means that students surpass teachers or future generations surpass predecessors.
Extended information 1. Source:
My understanding of cattle comes from Zhuangzi Health Master written by Zhuang Zhou in the pre-Qin Dynasty: "My understanding of cattle is that Wen Huijun, the touch of his hand, the leaning of his shoulder, the walking of his foot, the squatting of his knees, the sudden appearance and the sudden strike of his knife are all in tune."
Commentary: There is a chef named Ding who specializes in killing cows for Liang. Where his hands touched, where his shoulders rested, where his feet stepped, where his knees stood, his skin was raw, and the knife went in, making a louder noise. All these sounds are not against the rhythm.
According to You comes from Xunzi's "Xunzi's Persuasion to Learn" in the Warring States Period: "Green, take it from blue, green is blue."
Interpretation: cyan is extracted from blue, but the color is darker than blue.
Second, understanding:
"The function is completed, and my skills have been practiced for a long time; The road is at your feet, and Xunzi's suggestion to study and study shines on you. " There are two historical allusions in two sentences: an expert who knows cows, take care of you. Genius has always been a minority since ancient times, but most of the achievements have been made bit by bit. Students surpass teachers, apprentices surpass masters, and younger generations surpass predecessors, which shows that people can improve themselves through learning, and it is not difficult to surpass masters.
Baidu Encyclopedia-Zhiniu (China Idiom)
Baidu Encyclopedia-Shine on You (Idiom)