R. Joseph taught: "What is the meaning of the verse, 'And none of you shall go out at the door of his house until the morning?' (Exodus 12:22)¹ Once permission has been granted to the destroyer, he does not distinguish between the righteous and the wicked. Indeed, he even begins with the righteous."² Commenting on Exodus 33:5 ("If for a single moment I should go up among you, I would consume you"), the midrash says: "Yahweh means he could wax wroth with you for a moment -- for that is the length of his wrath, as is said in Isaiah 26:20, 'Hide yourselves for a little moment until the wrath is is past' -- and destroy you." Yahweh gives warning here of his unbridled irascibility. If in this moment of divine wrath a curse is uttered, it will indubitably be effective. That is why Balaam, "who knows the thoughts of the Most High," [Numbers 24:16] when called upon by Balak to curse Israel, was so dangerous an enemy, because he knew the moment of Yahweh's wrath.³

¹ A reference to the slaying of the first-born in Egypt.
² Nezikin I, Baba Kamma 60 (in The Babylonian Talmud, trans. and ed. by Isidore Epstein, p. 348).
³ Zera'im I, Berakoth 7a (Babylonian Talmud, ibid.)

Balaam's superiority over Balak and the other magicians lay in this, that he could accurately determine the moment in which God is wrathful, and it was for this reason that his curse was always effective because he knew how to curse at the very instant of God's anger. It is true that God is angry for one instant every day, to wit, during the third hour of the day, when the kings with crowns upon their head worship the sun, but this moment is of infinitesimally short duration. Fully eighty-five thousand and eighty-eight such moments make an hour, so that no mortal save Balaam had ever been able to fix that moment, although this point of time has its outward manifestations in nature, for while it lasts, the cock's comb becomes absolutely white, without even the smallest stripe of red.