法華義疏 1.74

1.74

以物有信心方乃說法，故知有如是佛說經時，即有侍者、聞法、時節、教主、住處、同聞，故知實有六事也。

Because beings have faithful minds, [the Buddha] only then preached the Dharma; thus we know that 'thus' was present. When the Buddha preached the scripture, there were the attendant, the hearing of the Dharma, the time, the master of the teaching, the dwelling place, and the co-listeners. Thus we know there were truly six matters.