“The sun rises and the sun sets, and it hastens to its place where it arises” (Ecclesiastes 1:5). “The sun rises.” Rabbi Berekhya said in the name of Rabbi Abba bar Kahana: Don’t we know that “the sun rises and the sun sets”? Rather, to what is it [alluding]?
Before the sun of one righteous individual sets, He causes the sun of another righteous individual to rise. The day that Rabbi Akiva died, Rabbi [Yehuda HaNasi] was born, and they read this verse in his regard: “The sun rises and the sun sets.” The day that Rav Ada bar Ahava died, Rav Hamnuna his son was born, and they read in his regard: “The sun rises and the sun sets.” The day that Rav Hamnuna died, Rabbi Avin his son was born, and they read in his regard: “The sun rises and the sun sets.”
The day that Rabbi Avin died, Abba Hoshaya of Teraya was born, and they read in his regard: “The sun rises and the sun sets.” Before the sun of Sarah set, the sun of Rebecca rose. That is what is written: “Betuel begot Rebecca” (Genesis 22:23), and then, “Sarah died in Kiryat Arba” (Genesis 23:2), and it is written: “Isaac brought her into the tent of his mother Sarah” (Genesis 24:67).30See Bereshit Rabba 60:16, where this verse is interpreted to mean that Rebecca was a worthy replacement for Sarah.
Before the sun of Moses set, the sun of Joshua rose. Before the sun of Joshua set, the sun of Otniel, who is Yabetz, rose. So it is with all of them in each and every generation; that is, “the sun rises and the sun sets.”