大方廣佛華嚴經疏 28.47

28.47

四十施連肉爪中，言赤銅相者，即是小相。五無比者，事爪則不染塵垢，智爪則不染境相。言善生者，善業生故。有云：西域方言，謂善生為端正。餘可知。所以求法偏語施爪者，一則以引例中有現事故。下入火求法，亦準此通。二有所表，以爪能爴取，順求義故。下入火求者，表難取故。故《智論》云「般若波羅蜜，猶如大火聚，四邊不可取，無取亦不取」故。

Forty: In giving the nails attached to the flesh, the phrase "marks of red copper" refers to minor characteristics. The five being peerless: the phenomenal nails are not defiled by dust and grime; the wisdom nails are not defiled by the marks of sensory objects. The phrase "well-born" is because they are born of good karma. Some say that in the dialect of the Western Regions, "well-born" means well-proportioned and handsome. The rest is intelligible. Why, in seeking the Dharma, does one specifically speak of giving the nails? First, it is because there is an actual event in the cited precedents. Entering fire to seek the Dharma below is also understood according to this. Second, it has a symbolic meaning: because nails can scratch and seize, it accords with the meaning of seeking. Entering fire to seek below symbolizes that it is difficult to grasp. Therefore, the Dazhidulun says: "Prajñāpāramitā is like a great mass of fire; it cannot be grasped from the four sides, and being ungraspable, it is also not grasped."