During the Sixteen Kingdoms period, Murong Chui, the fifth son of Former Yan ruler Murong Huang, repeatedly won great military honors, but his own royal family grew jealous, forcing him to flee and seek refuge with Fu Jian of Former Qin.
Fu Jian had long harbored ambitions to conquer the Former Yan, but he hesitated out of fear of Murong Chui. When he learned that Murong Chui had defected to him, Fu Jian was overjoyed, personally riding out to the city gates to welcome him with a grand ceremony. However, his prime minister, Wang Meng, saw that Murong Chui possessed extraordinary talent and ambition, and would never willingly submit to another's rule. Wang Meng urged Fu Jian, "You must kill him—he is too dangerous to keep alive." But Fu Jian refused, instead appointing Murong Chui as General of the Champion and Marquis of Bindu.
Later, Fu Jian suffered a devastating defeat at Huainan, losing most of his army—only Murong Chui's forces remained intact. Murong Chui then requested to station his troops at Ye, and Fu Jian agreed. Fu Jian's minister Quan Yi tried to dissuade him, warning, "Murong Chui is a renowned general, like Han Xin and Bai Qi of old. He harbors great ambitions and won't be content under anyone's thumb. Even granting him lands and titles wouldn't satisfy him—how could the title of Champion General be enough? Moreover, Murong Chui is like a hawk: when hungry, he comes to you; when full, he flies away. Given the chance, he'll surely pursue his lofty ambitions. You must rein him in now, before he acts on his whims." Fu Jian once again ignored his minister's advice.
Later, Murong Chui indeed raised his own banner and became the first ruler of the Later Yan dynasty.
The idiom "ji fu bao yang" means to cling when hungry and fly away when full. It later describes someone greedy, snobbish, and ungrateful.
Source: *Book of Jin*, "Biography of Murong Chui"
Meaning of the Idiom: Later, the Chinese idiom "饥附饱飏" came to describe how someone greedy, snobbish, and ungrateful.