瑜伽論記 12.296

12.296

如說乃至廣說者，引佛說證，以定力故放光普照，聲說普聞，準阿含經佛或有時為化梵眾，往彼天上身顯勝光，口宣妙法，諸梵見光，聞其所說不覩其形。

"As it is said... up to... extensively expounded": this cites the Buddha's teaching as testimony. By the power of meditative absorption, he emits light that shines everywhere, and the sound of his preaching is heard everywhere. According to the Āgama sūtras, the Buddha at times, in order to transform the Brahmā assemblies, would go to that heaven, displaying superior radiance with his body and proclaiming the wondrous Dharma with his mouth; the Brahmās saw the light and heard what he expounded, yet did not behold his form.