成唯識論述記 3.51

3.51

述曰：內種是因緣，必由熏習方能生果。法爾種子必由熏長，方能生果故；新熏熏生，方能生果，有情法故。

The Commentary states: Internal seeds are cause conditions; they must depend on perfuming to be able to produce results. This is because innate seeds must depend on perfumed growth before they can produce results; and newly perfumed seeds are produced through perfuming before they can produce results, because they are dharmas of sentient beings.