מדרש אויף ישעיהו 48:12

This is what Rabbi Yehoshua of Sikhnin says in the name of Rabbi Levi: Why are the names of the tribes not identical everywhere, but rather, at times this one precedes that one, and at times, that one precedes this one? It is so they would not say: The children of the wives are first and the children of the maidservants last, to teach you that these were not greater than those. Alternatively, why do these precede those? It is because they are the ceiling of the world. One who installs a ceiling properly places the thickness of this ceiling beam alongside one that is not its equal; therefore, this one precedes that one. From where is it derived that they are the ceiling [tikra] of the world? It is as Isaiah says: “Heed Me, Jacob and Israel, whom I called [mekora’i]” (Isaiah 48:12).

R. Joshua of Sikhnin said in the name of R. Levi: The names of the tribes are not mentioned in the same order in every instance. At various times one precedes the other. Why is that so? Lest people say that the children of Jacob’s wives take precedence over those of his handmaidens. This teaches us that one was not greater than another. Another comment on why one precedes another: They are, as it were, like the ceiling of the world; just as one constructs a ceiling by placing the thick side of one beam against the thin side of another, so on different occasions He mentioned one before the other. How do we know that they are the ceiling (tikrah) of the world? Because it is stated: Hearken unto Me, O Jacob and Israel, My called (mekora’) (Isa. 48:12).

R. Joshua of Sikhnin said in the Name of R. Levi: The names of the tribes are the same in every place, except that sometimes one takes precedence and sometimes another.²⁵The parallel version in Exod R. 1:6 reads: “Why are not the names of the tribes the same in every place, but sometimes….” Similarly, Tanh., Exod. 1:3. Why so? Lest the sons of the wives²⁶Literally: “ladies.” (Leah and Rachel) be written first and the sons of the bondmaidens (Zilpah and Bilhah) written last. So why does one <name> sometimes take precedence and sometimes come later? To teach you that the former were not greater than the latter. Then why do some take precedence over others? Because they are the ceiling of the world, and whoever puts in a proper roof sets the top (i.e. the thin end) of one beam next to the top of the other.²⁷The text is probably corrupt. Cf. the parallel in Tanh., Exod. 1:3: “And whoever prepares a proper ceiling sets the thick end of one beam next to the top of another since they are not equal.” So also Exod. R. 1:6. See Buber’s note here. Some < tribes >, therefore, take precedence over others. And where is it shown that they are the ceiling (rt.: QRH) of the world? Where it is stated (in Is. 48:12): LISTEN TO ME, O JACOB, EVEN ISRAEL, WHOM I HAVE CALLED (rt.: QR').