תַּ֣חַת שָׁ֭לוֹשׁ רָ֣גְזָה אֶ֑רֶץ וְתַ֥חַת אַ֝רְבַּ֗ע לֹא־תוּכַ֥ל שְׂאֵֽת׃
For three things the earth doth quake, And for four it cannot endure:
Find Mishnaic references to Proverbs 30:21: passages from the 63 tractates of the Mishnah that cite or discuss this verse, free.