法華論疏 2.239

2.239

而言相成就者，可相時而動，可語即語、宜默便默，故名為相。二者有利根眾生，聞上所說悟解相現，不須復說。故名為相。

Speaking of 'perfection of signs' means that one can act according to the time: if one should speak, one speaks; if it is suitable to be silent, one is silent; hence it is called 'signs.' Second, there are beings with sharp faculties who, hearing what was preached above, manifest signs of awakening and understanding, so that there is no need to speak further. Hence it is called 'signs.'