首楞嚴義疏注經 4.107

4.107

種謂已受愛取所潤，即異本之種也，故云流愛為種。胎即正約現行一念識心生起之時，然種即想愛俱為種，胎即想愛俱為胎，經文存略，故各舉一也。父母與子三處情想，互相交合，互相遘遇，引發吸取界趣同業，令歸一處，結成胎藏，故云交遘發生，吸引同業。自業為因，三處情想為緣。羯羅藍，云凝滑。遏蒲曇，云疱胎中前二七也。若至三七，胎卵即分，故約前二未分位說。

"Seed" refers to that which has already been moistened by love and grasping, which is the seed of distinct origins; hence it says "flowing love becomes the seed." "Womb" specifically concerns the very time when a single thought of the active conscious mind arises. Yet seed means that both thought and love serve as seed, and womb means that both thought and love serve as womb; the sūtra text abbreviates, and therefore mentions one for each. The emotions and thoughts of the parents and the child at the three places mutually intermingle and encounter each other, giving rise to and drawing in the shared karma of realms and destinies, causing them to return to a single place and coalesce into an embryonic womb; hence it says "intercourse and confluence bring forth occurrence, attracting shared karma." One's own karma is the cause, and the emotions and thoughts of the three places are the conditions. Kalala is called coagulated slipperiness. Arbuda is called a blister—these are the first two [periods of] seven days in the womb. If reaching the third [period of] seven days, womb-birth and egg-birth are differentiated; hence it is stated regarding the first two stages before differentiation.