Deuteronomy 4:10–11

10 Specially the day that thou stoodest before the LORD thy God in Horeb, when the LORD said unto me, Gather me the people together, and I will make them hear my words, that they may learn to fear me all the days that they shall live upon the earth, and that they may teach their children. 11 And ye came near and stood under the mountain; and the mountain burned with fire unto the midsta of heaven, with darkness, clouds, and thick darkness.