大般涅槃經義記 1.121

1.121

下第十一，如來化周，攝光歸口。前放六光，何故言五？此如上釋，頗梨、碼碯合為雜色，是以言五。又外國人相傳釋云「所放六中，留一傳法，故但收五。」前照十方，今此何故但言覆會？亦如上釋，隨其所照眾生故爾，示化已周，故從口入。

Below is the eleventh: the Tathāgata's transformation being complete, he withdrew the light into his mouth. Earlier he emitted six rays of light; why does it say five? This is as explained above: crystal and agate were combined into variegated color, which is why it says five. Furthermore, a transmission from foreigners explains: "Of the six emitted, one was retained to transmit the Dharma, so he only withdrew five." Earlier it illuminated the ten directions; why does it say here only that it covered the assembly? It is also as explained above: it was in accordance with the sentient beings illuminated, and to show that the transformation was already complete, it entered through the mouth.