daf bit: Avodah Zara 4

The g'mara is discussing whether and when God is wrathful. Abaye says that God is wrathful during the first three hours of the day, when the comb of the cock is white. (Later, he says, the comb is streaked with red.) R. Yehoshua ben Levi was being taunted by a min (a Jewish convert to Christianity). One day R. Yehoshua took a cock, placed it near his bed, and sat down to watch it, thinking: "when that hour arrives I will curse him". When that hour did arrive he was sleeping. He said: from this we can learn that it is not proper to act thus, for "His tender mercies are over all His works" (Ps. 145:9). (4b)