Kommentar zu Wajikra 15:31

והזרתם THUS SHALL YE PUT APART [THE CHILDREN OF ISRAEL] — The word נזר has wherever it occurs the meaning of "separating". Similar is (Isaiah 1:4) “they are gone away (נזורו) backward" ; (Genesis 49:26) “him that was separated from (נזיר) his brethren” (Sifra, Metzora Parashat Zavim, Chapter 9 6).

והזרתם את בני ישראל מטומאתם, “you shall separate the Children of Israel from their ritual impurities.” These additional words are the source for our sages having instructed husbands to separate from their wives when these are about to menstruate (Shevuot 18). As to the length of time a husband has to separate from his wife, Ravina said a 12-hour period. The Talmud Niddah 63 elaborates that if a woman was in the habit of seeing menstrual blood each month at midday, her husband has to stay away from her on that entire day, but he may cohabit with her on the preceding night. If she usually experiences this phenomenon in the second hour after daybreak, she is also still permitted to her husband on the preceding night. If, on the other hand, she usually notices such blood as beginning to flow during the night, even near daybreak, she is out of bounds for intercourse with her husband the entire night before that. However, she is permitted to her husband during the entire daylight period preceding that night. Even if she normally experiences a blood flow during the second hour of the night, her husband may still disregard her approaching menstruation until sunset before the night in question. According to theTalmud in Shevuot which we quoted, when a husband disregards these admonitions of the sages, his children (if not of age) even if of the excellence of the sons of Aaron, may be liable to die as a punishment for his lack of restraint. The sages derive all this from the admonition in our verse to separate themselves from contact with their contamination. Immediately after this paragraph the Torah reports (a second time) that the two older sons of Aaron had died. This may be taken as a warning. The sages have actually been warned by our verse to warn the people of the possible consequences of disregard of the instructions in this verse.

Separation. This is because the ז of והזרתם is stressed, bringing a נ before it, as if it is written, והנזרתם. Thus, the root of היזרתם is נזר (to abstain from).