(Exodus 24:17) "And the appearance of the glory of the LORD was like a devouring fire." Rabbi Shimon ben Yochai says: Come and see how harsh the power of transgression is. Before they stretched out their hands to sin, what is said of them? "And the appearance of the glory of the LORD was like a devouring fire" - yet they were not afraid and did not tremble. But once they stretched out their hands to sin, what is said of them? "And Aaron and all the children of Israel saw Moses, and they were afraid to come near him."
When Sin Made the Devouring Fire Fearsome
Yalkut Shimoni on Torah 362:8
(שמות כד יז) וּמַרְאֵה כְּבוֹד ה' כְּאֵשׁ אֹכֶלֶת. רַבִּי שִׁמְעוֹן בֶּן יוֹחַאי אוֹמֵר. בּוֹא וּרְאֵה כַּמָּה כֹּחַ עֲבֵרָה קָשֶׁה, שֶׁעַד שֶׁלֹּא פָּשְׁטוּ יְדֵיהֶם בָּעֲבֵרָה מַה נֶּאֱמַר בָּהֶן, וּמַרְאֵה כְּבוֹד ה' כְּאֵשׁ אֹכֶלֶת, לֹא יְרֵאִין וְלֹא מִזְדַּעְזְעִין, וּמִשֶּׁפָּשְׁטוּ יְדֵיהֶן בַּעֲבֵרָה מַה נֶּאֱמַר בָּהֶן "וַיַּרְא אַהֲרֹן וְכָל בְּנֵי יִשְׂרָאֵל אֶת מֹשֶׁה וַיִּירְאוּ מִגֶּשֶׁת אֵלָיו".