Thunder Lightning and the Five Voices of Sinai

Another interpretation: the matter is decided from its own context. "Go to the people and sanctify them today and tomorrow" (Exodus 19:10). If the concern were immersion, one could immerse on the fifth day and become pure at sunset. So what does Scripture teach by saying "Go to the people and sanctify them today and tomorrow"? Rather, the Omnipresent told Moses to separate them from women, as it is said, "Do not draw near to a woman" (Exodus 19:15). From here they said that a woman who emits semen on the third day is impure; the proof of the matter is from Sinai, the words of Rabbi Eleazar ben Azariah. Rabbi Ishmael says: sometimes it is four onot [time-periods], sometimes five, sometimes six. Rabbi Akiva says: always five. "And it came to pass on the third day" and so forth (Exodus 19:16): this teaches that the Holy One, blessed be He, agreed with him, to fulfill through him what is said, "While the king was at his table" and so forth (Song of Songs 1:12). "And there were voices" (Exodus 19:16): "voice of voices," kinds of sounds differing one from another. "And lightnings": one flash, many flashes [kinds of lightnings] differing one from another. "And a heavy cloud upon the mountain": this is the thick darkness, as it is said, "And Moses drew near to the thick darkness" (Exodus 20:18). "And the sound of a shofar very strong": the way of an ordinary person is that the longer he blows, the weaker his sound grows, but here the longer it went, the higher the sound rose. And why so? At the outset, to soothe the ear with what it was able to hear. "And all the people trembled" (Exodus 19:16): this teaches that they quaked. Rabbi Chelbo said: anyone who enjoys the feast of a bridegroom and does not gladden him is as though he transgresses the five voices, as it is said, "the voice of joy and the voice of gladness, the voice of the bridegroom and the voice of the bride, the voice of those who say, Give thanks to the LORD of hosts" and so forth (Jeremiah 33:11). And if he gladdens him, what is his reward? Rabbi Yehoshua ben Levi said: he merits the Torah, which was given with five voices, as it is said, "And it came to pass on the third day when it was morning," and it is written, "And the sound of the shofar."