法華義疏 7.200

7.200

答：聲聞本非佛種，今忽言是子則似如權引，故重有此實之言也。又前明初為父子時，今欲付子之財，故重言實是我子。

Answer: The śrāvakas were originally not of the Buddha-lineage; suddenly declaring now that they are his sons would seem like a provisional enticement, so he repeats this word "truly." Furthermore, earlier he explained the time when they were originally father and son; now he wishes to entrust the son with the wealth, and therefore repeats that he is truly his son.