TT #63 · Parshas Shemini · Aliyah 3 · Passuk 10
Chabad.org — Vayikra Chapter 10 with Rashi
Shevuot 18b.
E-Daf.com — Shevuot 18b (Tsurras Hadaf)
English: “And to distinguish.” Rabbi Yehoshua ben Levi teaches that one who separates from his wife near the onset of her menstrual period will have children fit for teaching, based on the connection between “to distinguish” and “to teach.”
Textual linkage — the teaching is derived from the wording or structure of the verse.
The verse is read as rewarding careful separation near the onset of menstruation with children fit to teach.