“The parable of the sparrow” is indicated by the word “nirgrantha-srava-ka-cataka-vat” in the ninth chapter of the Abhidharmakosa-bhasya (AKBh). The commentary on this word by Yasomitra forms one story that contains a question and an answer. It is similar to one of Aesop's Fables called “κακοπραγμον”which means “an evil doer.” This seems not have been identified among the Buddhist canons. The interpretation of “avyakrta” in this chapter is examined by referring to this story.
In this story, the evil doer is a questioner. The section that includes the word in the AKBh discusses “avyakrta.” The Buddha is reported to have not expressed an opinion on a series of questions such as “Is the world eternal ” Relying on this, the Vatsiputriyas insist on “avaktavya.” They don't state whether an individual (pudgala) is exactly the same as elements (skandha).
The point of the critique by Vasubandhu (the author of AKBh) is taking “prastur asaya” (the intentio n of the questioner) as the reason for “avyakrta”. Therefore, if a questioner does not have “asaya,” those questions should be answered. The parable of the sparrow is quoted to emphasize “asaya.”