וּמַרְאֵה֙ כְּב֣וֹד יְהוָ֔ה כְּאֵ֥שׁ אֹכֶ֖לֶת בְּרֹ֣אשׁ הָהָ֑ר לְעֵינֵ֖י בְּנֵ֥י יִשְׂרָאֵֽל׃
And the appearance of the glory of the LORD was like devouring fire on the top of the mount in the eyes of the children of Israel.
Read kabbalistic (mystical) interpretation of Exodus 24:17: and classical mystical sources.