Of the 52 times that the word solet appears in the Bible, more than half of those are in the Book of Numbers, mostly clustered in Parashat Nasso and Parashat Pinchas.
The Torah refers to the cereal grains used for meal-offerings with the word solet, with two exceptions: when discussing the Omer offering (Lev. 23:10–11) and the Sotah offering (Num. 5:15). In the latter case, the word kemach is used instead of solet. The Omer and Sotah offerings are both brought from barley/kemach, while all other meal-offerings are brought from wheat/solet.
Based on this, Rashi (to Lev. 2:1) and Rashbam (to Gen. 18:6) maintain that the solet always implies “wheat flour,” thus accounting for this word’s absence from the Omer and Sotah offerings. Nevertheless, Rabbi Shlomo Pappenheim (1740–1814) points out we find the term solet-chitim (solet of wheat) (Ex. 29:2), implying that the solet on its own does not necessarily imply mean wheat.
Either way, when the Sotah offering is explicitly said to come from kemach, it refers to a grade of flour rather than a different species of grain.
Donash Ibn Labrat (920–990) writes a diatribe against Menachem Ibn Saruk (920-970) that one can look to Arabic to understand the meaning of words in Hebrew. An example is the Hebrew word kemach (which appears 14 times in the Bible) having an ostensible Arab cognate meaning wheat, as opposed to barley.
However, an anonymous student of Menachem defends his teacher by noting that kemach in Arabic means “wheat” in general, while kemach in Hebrew refers specifically to wheat that has been ground, i.e., flour.
That said, Donash’s student Ibn Sheshet concedes that in the case of the Sotah’s meal-offering where the Torah uses the rase kemach-seorim (“kemach of barley”), the word kemach cannot possibly refer to wheat like it does in Arabic.
The Mishnah (Menachot 6:7) teaches that the process yielding the finest solet for various meal-offerings involved sifting the flour multiple times (see Rashi to Menachot 76b).
Rabbi Samson Raphael Hirsch (to Gen. 18:6) clarifies that the difference between kemach and solet is not in how fine or coarse the flour is but that the main difference between kemach and solet is not how finely it is ground but whether the flour is whole – that is, whether the bran and wheatgerm are removed. White flour (solet) consists of only the endosperm of the wheat kernel; while whole wheat flour (kemach) includes the husks and fibers.
Kemach can still refer to “fine flour,” depending on how well it is ground, still containing within its granules such impurities as the husks/bran and other fibers (see Rashi to Ketubot 112b). Like Rashi (to Sotah 14a) points out, “everything” is mixed into kemach. Accordingly, solet refers to white flour, which is typically lighter and less coarse than kemach because it is free from heavier particles like bran.
This type of flour was often sifted time and again so that only the finest flour was left. Rashi (to Taanit 9b) explains that first the finer white flour would pass through the sifter, and only afterwards would the coarser whole-wheat flour pass through (see also Tosafot there). The Mishnah (Avot 5:15) alludes to this process by saying, “A sifter filters out the kemach and only keeps the solet.” Rashi (to Bava Metzia 87a) writes that solet is “better” than kemach.
Similarly, the Talmud uses the expression “he doesn’t care about his kemach” (Yevamot 42b, Pesachim 84a, Sukkah 54a) to criticize a person who is not careful to speak precisely. As Rashi explains it, such a person disregards the quality of his speech, as if he is grinding kemach (as opposed to solet).
The Talmud (Kiddushin 69b) says that before Ezra left Babylonia for the Holy Land, he ensured that the Jews who remained in Babylonia were of impeccable lineage, such that the Jewish community there was considered like “pure solet” vis-à-vis the “mixed dough” that was the Jewish community in the Holy Land.
Rabbi Yehudah Aryeh of Carpentras writes in Ohalei Yehuda that the word kemach is derived from a combination of the roots kuf-mem-hey (“standing,” “erect”) and mem-chet-hey (“erasure,” “destruction”), as the grinding process takes the once-proud stalk of wheat that stood erect in the field and cuts it down to size to produce flour: The word kamah (Ex. 22:5, Peah 2:7, 4:7, 5:2, Menachot 10:9) denotes uncut grain that “stands” in the field. Alternatively, he explains the kemach as derived directly from the root yod-mem-chet (“erasure,” “destruction”), based on the interchangeability of the letters kuf and yod.
Interestingly, the Babylonian Talmud connects the word kemach to Kimchit, a pious woman named Kimchit, who merited that each of her seven sons would function as a Kohen Gadol because she was careful to always cover her hair. In lauding the high quality of Kimchit’s offspring, the rabbis said: “All kemach yields [naught but] kemach, but Kimchit’s kemach is solet” (Jerusalem Talmud Yoma 1:1 and Bamidbar Rabbah §2:26).
We find another kemach-related reference to names in the illustrious Kimchi family, famous for producing such great Hebrew grammarians as Rabbi Yosef Kimchi (1105-1170) and his two sons Rabbi David Kimchi (1160-1235) and Rabbi Moshe Kimchi (1120-1190),
Rabbi Pappenheim traces the word solet to the biliteral root samech-lamed, which refers to “repeated actions.” One usage is sal, referring to a bread basket (see Gen. 40:16, Lev. 8:2), which is used constantly. He accordingly proposes that solet refers to flour that is considered so valuable and treasured that it is not dumped into a sack like the less precious kemach. Alternatively, he explains that the word solet invokes the repeated pressing, grinding, and crushing necessary to produce high-quality flour.