仁王經疏 2.123

2.123

問：經說九諦，如何言八？答：經意欲顯妙覺勝故，開為二諦；論意欲明同大乘故，合為一數。前之七諦，通大小故，故今此經依八諦說。

Question: The sūtra speaks of nine truths; why does it say eight? Answer: The intention of the sūtra is to reveal the excellence of wondrous awakening, so it divides them into two truths; the intention of the treatise is to clarify the commonality with the Mahāyāna, so it combines them into a single count. The preceding seven truths are common to both the Great and Small [Vehicles]; therefore, this sūtra now speaks on the basis of eight truths.