Concerning the Ten Commandments, which are the Heads of the Law (44-46)

And, moreover, as was natural, he filled the whole place with miraculous signs and works, with noises of thunder too great for the hearing to support, and with the most radiant brilliancy of flashes of lightning, and with the sound of an invisible trumpet extending to a great distance, and with the march of a cloud, which, like a pillar, had its foundation fixed firmly on the earth, but raised the rest of its body even to the height of heaven; and, last of all, by the impetuosity of a heavenly fire, which overshadowed everything around with a dense smoke. For it was fitting that, when the power of God came among them, none of the parts of the world should be quiet, but that everything should be put in motion to minister to his service.

And the people stood by, having kept themselves clean from all connection with women, and having abstained from all pleasures, except those which arise from a participation in necessary food, having been purifying themselves with baths and ablutions for three days, and having washed their garments and being all clothed in the purest white robes, and standing on tiptoe and pricking up their ears, in compliance with the exhortations of Moses, who had forewarned them to prepare for the solemn assembly; for he knew that such would take place, when he, having been summoned up alone, gave forth the prophetic commands of God.

And a voice sounded forth from out of the midst of the fire which had flowed from heaven, a most marvellous and awful voice, the flame being endowed with articulate speech in a language familiar to the hearers, which expressed its words with such clearness and distinctness that the people seemed rather to be seeing than hearing it.