וַיְהִ֣י ׀ בִּשְׁלֹשִׁ֣ים שָׁנָ֗ה בָּֽרְבִיעִי֙ בַּחֲמִשָּׁ֣ה לַחֹ֔דֶשׁ וַאֲנִ֥י בְתֽוֹךְ־הַגּוֹלָ֖ה עַל־נְהַר־כְּבָ֑ר נִפְתְּחוּ֙ הַשָּׁמַ֔יִם וָאֶרְאֶ֖ה מַרְא֥וֹת אֱלֹהִֽים׃
Now it came to pass in the thirtieth year, in the fourth month, in the fifth day of the month, as I was among the captives by the river Chebar that the heavens were opened, and I saw visions of God.
Shenei Luchot HaBerit
Know - that the pious one (R. Yosef Karo) and I agreed to make a great effort on the night of Shavuot, and to keep sleep from our eyes. Praise to God, so it was. We didn't stop one moment - listen, and your soul will be revived...