法華義疏 11.158

11.158

表說法事竟故攝舌相，欲令十方通徹彼此相見故不收光。《涅槃經》表所作已辦故收光也。

To signify that the matter of preaching the Dharma was finished, he drew in the mark of the tongue; wishing to keep the ten directions fully transparent and allow those here and there to see one another, he did not retract the light. In the Nirvāṇa Sūtra, to signify that what was to be done had already been accomplished, he retracted the light.