(Exodus 32:1-6) "And the people saw that Moses delayed [boshesh]." Do not read "delayed" [boshesh] but rather "the sixth has come" [ba'u shesh]. When Moses ascended to the heights, he said to Israel: at the end of forty days, at the beginning of the sixth hour, I will come. At the end of forty days Satan came and threw the world into confusion. He said to them: where is Moses your teacher? They said to him: he ascended to the heights. He said to them: the sixth hour has come, and they paid him no heed. He said: he has died, and they paid him no heed. He showed them an image of his bier in the cloud, and this is what they said, "for this Moses, the man, we do not know what has become of him."
How Satan Tricked Israel About the Sixth Hour Before the Calf
Yalkut Shimoni on Torah 391:7
(שמות לב א-ו) וַיַּרְא הָעָם כִּי בֹשֵׁשׁ מֹשֶׁה. אַל תִּקְרֵי 'בֹשֵׁשׁ' אֶלָּא 'בָּאוּ שֵׁשׁ', בְּשָׁעָה שֶׁעָלָה מֹשֶׁה לַמָּרוֹם אָמַר לְיִשְׂרָאֵל לְסוֹף אַרְבָּעִים יוֹם בִּתְחִלַּת שֵׁשׁ אֲנִי בָּא, לְסוֹף אַרְבָּעִים יוֹם בָּא שָׂטָן וְעִרְבֵּב אֶת הָעוֹלָם, אָמַר לָהֶן, מֹשֶׁה רַבְּכֶם הֵיכָן הוּא, אָמְרוּ לוֹ עָלָה לַמָּרוֹם, אָמַר לָהֶם בָּאוּ שֵׁשׁ, וְלֹא הִשְׁגִּיחוּ עָלָיו, מֵת, וְלֹא הִשְׁגִּיחוּ עָלָיו, הֶרְאָה לָהֶם דְּמוּת מִטָּתוֹ בְּעָנָן וְהַיְינוּ דְקָאָמְרֵי כִּי זֶה מֹשֶׁה הָאִישׁ לֹא יָדַעְנוּ מֶה הָיָה לוֹ.