וַיִּרְא֣וּ בְנֵֽי־יִשְׂרָאֵ֗ל וַיֹּ֨אמְר֜וּ אִ֤ישׁ אֶל־אָחִיו֙ מָ֣ן ה֔וּא כִּ֛י לֹ֥א יָדְע֖וּ מַה־ה֑וּא וַיֹּ֤אמֶר מֹשֶׁה֙ אֲלֵהֶ֔ם ה֣וּא הַלֶּ֔חֶם אֲשֶׁ֨ר נָתַ֧ן יְהוָ֛ה לָכֶ֖ם לְאָכְלָֽה׃
And when the children of Israel saw it, they said one to another: a‘What is it?’—for they knew not what it was. And Moses said unto them: ‘It is the bread which the LORD hath given you to eat.
Read kabbalistic (mystical) interpretation of Exodus 16:15: and classical mystical sources.