法華義疏 8.255

8.255

有人言：佛顏有舒斂，故知受不受。有人言：身光上下表之，故有受不受。有人言：初成道時佛有唱號默然者便是受請，涅槃時默然者便不受請。

Some say: the Buddha's countenance has relaxation and tension, and thus one knows whether he accepts or does not accept. Some say: the upward or downward movement of the bodily light indicates it, and thus there is acceptance or non-acceptance. Some say: when he first attained the Way, if the Buddha had someone announce his title and was silent, that was accepting the request; at the time of nirvāṇa, being silent was not accepting the request.