大毘盧遮那成佛經疏 10.69

10.69

次釋迦如來入于寶處三昧。寶從彼出，名為寶處。猶如大海出種種寶，若至彼洲，則隨意所須無所不足也。佛入此三昧已，從其面門出種種光，光中現此真言，乃至普遍一切佛剎。餘真言當知皆如此說也。

Next, Śākyamuni Tathāgata enters the Ratnasambhava samādhi. Jewels come forth from there, so it is named 'treasure-source' (ratnasambhava). Just as the great ocean produces various jewels, if one reaches that isle, then according to whatever one requires, nothing is lacking. After the Buddha entered this samādhi, from the portal of his face he emitted various lights, in which this mantra appeared, extending everywhere to all buddha-kṣetras. One should know that the remaining mantras are all spoken in this way.