大般涅槃經集解 2.35

2.35

Sengliang states: The sound reached the Summit of Existence, speaking of its being heard above. The light pervaded the ten directions, speaking of its fourfold distance. The two passages alternate with each other, but what they express is not different.
Fayao states: The light emitted from his mouth expresses the mark of the most ultimate, wondrous teaching.
Sengzong states: This is the second mark. Above, understanding was generated through sound; here, awakening is attained through light. "Gate" takes passage as its meaning; hence the mouth is the gate of the face.
Baoliang states: Regarding the lights of various colours: past sūtras also had this auspicious sign, but the one who produced the sūtra expressed the Buddha's majestic radiance; hence it is named "various".
Zhixiu states: Previously, although they heard the voice, they did not know where [it came from]; therefore he emitted light to show them and make them know.