The torah tells us that God spoke out of the fire in Devarim 4:36:
מִן-הַשָּׁמַיִם הִשְׁמִיעֲךָ אֶת-קֹלוֹ, לְיַסְּרֶךָּ; וְעַל-הָאָרֶץ, הֶרְאֲךָ אֶת-אִשּׁוֹ הַגְּדוֹלָה, וּדְבָרָיו שָׁמַעְתָּ, מִתּוֹךְ הָאֵשׁ.
Out of heaven He made thee to hear His voice, that He might instruct thee; and upon earth He made thee to see His great fire; and thou didst hear His words out of the midst of the fire.
Sh'mot Rabbah 5:9 quotes this but does not compare the torah itself to fire. (For other sources that do, see this answer.)
Sh'mot Rabbah does talk about the 70 languages:
It says: And all the people perceived the thunderings (Ex. XX, 15). Note that it does not say ‘the thunder ‘, but ’the thunderings‘; wherefore R. Johanan said that God's voice, as it was uttered, split up into seventy voices, in seventy languages, so that all the nations should understand. When each nation heard the Voice in their own vernacular their souls departed, save Israel who heard but who were not hurt. (Soncino translation)
Sh'mot Rabbah was probably compiled in the 12th century CE, so had benefit of the talmudic sources already cited in another answer. Sefaria has it in Hebrew, but I didn't find it in English online from a reliable source. (I cut/pasted from a collection that Soncino sells digitally. Translations should also exist in print books, which you might find listed as "Exodus Rabbah" or "Sh'mot Rabbah".)