וַיְהִ֤י הַשֶּׁ֙מֶשׁ֙ בָּ֔אָה וַעֲלָטָ֖ה הָיָ֑ה וְהִנֵּ֨ה תַנּ֤וּר עָשָׁן֙ וְלַפִּ֣יד אֵ֔שׁ אֲשֶׁ֣ר עָבַ֔ר בֵּ֖ין הַגְּזָרִ֥ים הָאֵֽלֶּה׃
日頭已經落下，天色一片漆黑；看哪，有冒煙的爐和燃燒的火把，從這些劈開的肉塊中間經過。
Zohar Chadash
But before the five covenants were given, there was only the covenant with fire, as it is stated (Genesis 15:17), “and behold, a smoking furnace and a flaming torch, etc.” And it is written (Genesis 15:18), “On that day the Lord made a covenant with Avram, saying.” But the fire was a covenant at first. And this is [the meaning of] Bereishit - take out fire (esh) from there, and brit (covenant) remains. Meaning to say, brit esh (a covenant of fire).