During the Five Dynasties period, Han Xizai, son of a military family, fled to the Wu Kingdom in the south after his father was executed by Emperor Mingzong Li Siyuan.
Han Xizai's close friend Li saw him off as he was leaving. The two drank heartily. Han Xizai said to Li, "If the state south of the Yangtze appoints me as chancellor, I will surely lead an army north and pacify the Central Plains."
After hearing this, Li believed that in such chaotic times, a wise bird should choose its tree wisely. Emboldened by wine, he declared loudly, "If any central kingdom would make me their prime minister, taking Jiangnan would be as easy as reaching into one's pocket."
Shortly after Han Xizai defected to the Wu Kingdom, it was conquered by the Southern Tang. Yet with corrupt officials in power there too, he never gained high office. Drowning his sorrows in wine and spending his days with singing girls, his earlier vow to become prime minister naturally never came to pass.
Li, on the other hand, became a general of the Later Zhou in the north, earning considerable military merit in the campaign against the Southern Tang, yet his vow to become prime minister remained unfulfilled.
The idiom "taking something out of a bag" means reaching into a pocket to retrieve an item, metaphorically describing something extremely easy to accomplish.
Source: *New History of the Five Dynasties*, "Biography of the Southern Tang"
Meaning of the Idiom: Later, the Chinese idiom "探囊取物" came to describe how reaching into a pocket to retrieve an item, metaphorically describing something extremely easy to accomplish.