In the idiom "throwing a brick to attract jade" (pāo zhuān yǐn yù), "pāo" means to throw or cast. It literally means throwing out a brick in order to draw back a piece of jade. It is commonly used as a humble expression to describe offering one's own crude, immature opinions or writings in the hope of eliciting superior insights or fine works from others. "Jīzǐ" refers to an unfired brick, i.e., a raw earthen block.
This idiom originates from the Song Dynasty text Jingde Chuandeng Lu (Jingde Era Record of the Transmission of the Lamp), Volume 10, "Chan Master Congshen of Zhaozhou's East Courtyard": "When the assembly gathered in the evening, the Master said: 'Tonight, anyone who understands my words may step forward.' At that moment, a monk stepped forward and bowed. Master Congshen said: 'I was just throwing a brick to attract jade, yet all I've drawn is a lump of raw brick!'"
The eminent Tang Dynasty monk Master Congshen had presided over the Guanyin Monastery in Zhao Prefecture for many years. Legend has it that he imposed extremely strict requirements on his disciples' meditation practice: each monk must sit quietly, calm their minds, concentrate fully, and completely ignore any external distractions, achieving a meditative state of mental stillness, cessation of delusive thoughts, and complete physical and mental immobility. One evening, when the monks gathered for their usual meeting, Master Congshen deliberately announced: "Tonight, anyone who comprehends the Dharma may step forward."
At such a moment, all disciples should have been sitting cross-legged, eyes closed, minds focused, motionless and steady. Yet one young monk could not contain himself; he actually stepped forward, assuming the role of one who understood, and bowed to the master. Master Congshen glanced at him and said slowly, "I was merely throwing a brick to attract jade, but instead I've attracted a lump of clay worse than a brick!"
There is another story associated with "throwing a brick to attract jade." According to historical records such as Lidai Shihua (Poetic Remarks Through the Ages) and Tan Zheng (Discussions and Proofs), the Tang poet Zhao Gu earned praise from the great poet Du Mu for his beautiful line "A long flute sounds, a man leans on a tower," leading people to nickname him "Zhao Leaning-on-the-Tower." At that time, another poet named Chang Jian deeply admired Zhao Gu's poetic talent. Hearing that Zhao Gu was traveling to the Wu region, Chang Jian guessed he would surely visit Lingyan Temple. So Chang Jian arrived at Lingyan first and inscribed two lines of a poem on the temple's front wall, hoping that Zhao Gu would see them and add two more lines to complete the poem. Sure enough, when Zhao Gu visited Lingyan Temple and saw the two lines on the wall, his poetic inspiration surged, and he spontaneously added two lines, completing a full quatrain. Since Chang Jian's lines were not as good as Zhao Gu's, his act of using an inferior poem to draw out a superior one from Zhao Gu became known as "throwing a brick to attract jade." In fact, Chang Jian and Zhao Gu were not contemporaries—their active periods were over a century apart—so the story of the poem continuation is not credible. However, because this tale is so well-known, people have accepted it as one of the origins of the idiom "throwing a brick to attract jade."