成唯識論述記 8.86

8.86

述曰：牽引、生起二因之內，雖復亦有非能生因，以業種等非能生故。此二因中因緣種子，一、親辨體；二、受果無盡，勝故，偏說是能生因，不說增上業種所攝。

The Commentary states: Although within the projecting and generating causes there are also things that are not productive causes (since karmic seeds and the like are not productive causes), the seeds that are cause-conditions within these two causes: first, directly establish the essence [of the effect]; second, receive fruits without end. Because they are superior, they are specifically spoken of as productive causes, and their subsumption under dominant karmic seeds is not mentioned.