The earliest source for this is found in Chassidic works. In Sefer HaMiddot of Rabbi Nachman of Breslov (entry “House,” Part II, §8), he writes: “As a segulah, when one enters a new house to live there, he should bring in a sword, a knife, or another weapon.” He gives an allusion to this in the verse, “Through wisdom a house is built” (Proverbs 24:3), together with “the weapons of violence are their swords” (Genesis 49:5). He repeats this teaching there (entry “Segulah,” Part II, §9).
In truth, there are additional reasons for this, for it is known that a knife cuts off harmful forces. Thus, Sefer Shiurei Taharah (Gross, ch. 33, p. 694) cites a segulah in the name of Rabbi Chaim of Volozhin: a woman who wishes not to miscarry should purchase a knife on the day of her immersion, take it with her to the mikveh, and at the time of the mitzvah place it beneath her pillow; afterward, she should keep it with her throughout the days of her pregnancy. [Later authorities wrote that this may be done with a small pocketknife.] Later authorities supported this from what is explained by the poskim: a woman whose night of immersion occurs when her husband is not in town should place a knife beneath her pillow. This is also what Rabbi Yosef Chaim wrote in Ben Ish Chai: one should take a knife during bedikat chametz in order to remove harmful forces. This also explains what is cited in the name of the Baal Shem Tov, z”l, that one does not give a knife as a gift—that is, one should not give a knife to his fellow as a present. This is cited in Sichot HaRan (§9). From all the above, it appears that a knife has the property of removing harmful forces, for a knife made of iron cuts off the external forces.
An additional reason may be suggested based on what is written in Kol Bo (siman 31, 25c): “One sharpens the knife every Erev Shabbat,” as is taught in the Sifrei: “And you shall know that your tent is at peace” (Job 5:24)—this refers to sharpening a knife. I found written in the name of Sefer Chayei Olam (which is Rabbeinu Yonah’s Sefer HaYirah, §309) that this is derived from the verse, “And they shall prepare that which they bring” (Exodus 16:5), where “that” is like “plowshares” and “pruning hooks” (Isaiah 2:4). This is cited by the Beit Yosef (siman 250), and the Rema likewise rules in his glosses to the Shulchan Aruch (siman 250, סעיף 1) that one should sharpen the knife on Erev Shabbat, for this is in honor of Shabbat, as one prepares himself for eating (Kol Bo and Beit Yosef in the name of Sefer Chayei Olam). End quote. Likewise, in Meshivat Nefesh (Exodus 16:5), this is cited in the name of the early authorities, from what the Torah states there: “And it shall be on the sixth day, and they shall prepare.” Our early authorities derived from here that one should sharpen the knife on Erev Shabbat, so that it will be properly sharp for cutting on Shabbat, as it says, “that which they bring”; “that” is related to “plowshares,” as it says, “They shall beat their swords into plowshares,” etc., and likewise, “their spears into pruning hooks.” See there. This is from the above-mentioned words of Rabbeinu Yonah.
From all the above, it appears that the very presence of a sharpened knife in the home is a sign of shalom bayit. This provides support for bringing a new knife into the home, since it is presumably sharpened properly, which is a sign of shalom bayit.
May it be Hashem’s will that you merit a good and settled dwelling in your home, and that joy and blessing rest there, both spiritually and materially.
Netanel Yisrael Ohana
This response was translated automatically from Hebrew and has not yet been reviewed by a person. Therefore, it may contain inaccuracies and should not be considered a definitive reference.
