Numbers 9:16 Midrash

כֵּ֚ן יִהְיֶ֣ה תָמִ֔יד הֶעָנָ֖ן יְכַסֶּ֑נּוּ וּמַרְאֵה־אֵ֖שׁ לָֽיְלָה׃

So it was alway: the cloud covered it, and the appearance of fire by night.

Read midrashic interpretation of Numbers 9:16: and classical rabbinic exegesis.