The Taught Lists, 46th Day of Spring, 525 M.E. (Electra): Bing Ding Tongzi was the Chinese god of fire. The name of the deity came from the phrase used to denote the boy responsible for lighting the monastery's lanterns in the evening.  So the Chinese term Bing Ding Tongzi was been translated as the "god of fire" or "fire boy" or "boy of fire."

One day, Chan Master Fayan asked his student, Bao'en, "From where did you come here?"

Bao'en said, "From Master Quinfeng."

Fayan asked, "What does Quinfeng teach?"  

Bao'en said, "Once, when I asked 'What is this student's true self?,' Quinfeng answered 'Bing Ding comes looking for fire'."  

Fayan told him that was an excellent answer, but added that Bao'en probably didn't understand it.

Bao'en said "Oh, I understood it alright. Bing Ding is fire, and fire looking for fire is like the self looking for the self." 

Fayan said, "Oh, I knew you didn't understand it."

When Bao'en asked how Fayan understood it, Fayan told him to ask him the question, so Bao'en asked, "What is this student's true self?" 

Fayan said, "Bing Ding comes looking for fire."

At these words, Bao'en was greatly enlightened.

If you understand this story, then, well, you don't. You're like Bao'en hearing the words from Quinfeng. You're lost in intellectualization, in ideation. 

Zen Master Dogen liked this story and in the year 1231 included it in Bendowa, the first charter of his Shobogenzo (yes, I'm still on the first chapter of Tanahashi's translation of Shobogenzo; only 95 more chapters left to go). Five years later, Dogen read a version of this story to his assembly at Koshoji Temple, and said, "Previously, the fire boy came seeking fire. Afterwards again the fire boy came seeking fire. Previously, why was he not enlightened but flowed down the path if intellection? Afterwards, why was he greatly enlightened and cast away the old nest? Do you want to understand?"  

After a pause, Dogen said, "The fire boy comes seeking fire. How much do the pillars and lanterns care about the brightness? The fire is covered with cold ashes and while searching we don't see it. Lighting it and blowing it out again gives birth to practice."    

Another time, Dogen said, "The fire boy comes seeking fire. With complete dedication, do not stop when you have only seen the smoke."