The famous Taz and the bread of Ammon and Moav
לא-יבא עמוני ומואבי בקהל יקוק גם דור עשירי לא-יבא להם בקהל יקוק עד-עולם: על-דבר אשר לא-קדמו אתכם בלחם ובמים בדרך בצאתכם ממצרים וגו’
An Ammonite or a Moabite may not marry into the congregation of Hashem. Even the tenth generation shall not marry into congregation of Hashem, forever. [This is] for the matter in which they didn’t greet you with bread and water as you departed from Egypt…
Although marriage with a non-Jew is forbidden, obviously if someone converted to Judaism they can marry into the fold. However, some nations have restrictions on who or when they can marry. For example, an Egyptian or an Edomite may only marry into the congregation after three generations of being Jewish. In contrast, the Torah forever forbids the nations of Ammon and Moav from marrying into the Jewish people, even if they converted sincerely. Even their descendants are restricted. Why is this? The Torah says it’s because they didn’t greet us with bread and water. The implication is that had they given it to us, we would have been permitted to eat it.
There is a somewhat known halacha that the bread of a non-Jew, even though it is completely kosher, is forbidden for a Jew to consume. Although some authorities are lenient in certain cases with bread from a non-Jewish baker, everyone forbids bread that was baked by an individual non-Jew. Obviously this shouldn’t present a contradiction with the bread of Ammon and Moav, as we’re discussing a later Rabbinic decree against the bread of a non-Jew. The Rabbis forbade this bread out of concern that it would lead to too much intermingling and intermarriage. Nevertheless, there are authorities who note that there does seem to be a conflict with this Rabbinic decree and the bread of Ammon and Moav.
There’s a much discussed innovation of Rav Dovid Segal in his well-known commentary Turei Zahav, known as the Taz on Shulchan Aruch. He says that if the Torah explicitly permits something, then the Rabbis wouldn’t decree against it. Some say it’s they were concerned that the Jewish people wouldn’t listen to their decree, since it contradicts the Torah. Others say it’s because it gives fuel to those who deny Rabbinic Judaism, as they can use the Torah as proof that the Rabbis are wrong in their decrees. Either way, this rule seems to not fit with our verse. Why?
The Torah tells us that the bread of Ammon and Moav, non-Jewish nations, would have been permitted for us to consume. If so, according to the Taz, the Rabbis wouldn’t then decree against its consumption. How then can there in fact be such a decree? Different approaches are suggested. Some say that the Taz’s rule is referring to when the Torah tells us not to be concerned about something, and therefore permitted it, in which case the Sages wouldn’t forbid it. However, if there was some side concern, like with non-Jewish bread and intermarriage, they would forbid it.
Others suggest that the Taz only meant that the Sages wouldn’t completely uproot something the Torah permitted. If, on the other hand, the Sages only partially forbade something, then it would be fine. For example, although the Sages forbade the bread of a non-Jew, they permitted the bread of a non-Jewish baker. Although, the simplest answer is that the Torah never actually permitted the bread of Ammon and Moav. It simply said they should have offered us bread. Who said we would have eaten it? They should have offered it as a matter of good will, regardless of our reaction.
Others make this question a non-starter. In truth, we didn’t even need the bread of Ammon and Moav. We had the Heavenly munn, and the magical well of water that accompanied us in the wilderness. If so, why would Ammon and Moav be so severely punished for not offering us what we already had? As a result of this question, some suggest a more metaphoric approach to what the Torah says. The Zohar tells us that if you greet someone on a journey warmly, offer them a smile, share with them a good word, it’s as if you fed them bread and water. Ammon and Moav were punished for not offering us a good word.
We see then that the Torah wasn’t speaking about literal bread, so the question on the Taz doesn’t get started. We also see that how severe the punishment is for not offering someone a good word. The consequences are grave for all of their descendants, for all time. All the more so must be the positive effect and reward for actually offering someone a good word.
 Based on a shiur by Rav Daniel Glatstein, found at https://www.torahanytime.com/#/lectures?v=90711
 Deuteronomy 23:4,5. See also Maharam Shif’s Derushim Nechmadim parshas Ki Seitzei Al Davar
 To be honest, I don’t see this implication. Although this is the assumption of the authorities that will be quoted below, we’ll see in the end that others also reject this implication as a way to avoid the issues raised with it
 Shulchan Aruch Yoreh Deah 112:2
 Rav Dovid Cohen of Flatbush wrote an entire sefer on the topic, called Taz HaYaduah
 He writes it in three places: Taz to Shulchan Aruch Orach Chaim 588:5, Yoreh Deah 117:1, and Choshen Mishpat 2 s.v. ולא לעבור. The Meiri to Megillah 4a s.v. יש שואלין brings the same principle as the Taz. The Chasam Sofer to Shulchan Aruch loc. cit. and in Teshuvos Chasam Sofer Yoreh Deah § 108 says another earlier source than the Taz is the Kessef Mishnah to Mishneh Torah Hilchos Melachim 3:7, brought by the Tosafos Yom Tov to Sanhedrin 2:2. Rabbi Akiva Eiger ad. loc. says it’s also in Tosafos to Bava Metzia 70b s.v. תשיך לא סגי. However, in Teshuvos Rabbi Akiva Eiger 1:74 he says that Tosafos and the Kessef Mishnah aren’t a proof for the Taz, as they’re discussing when the Torah explicitly commands to do something, not when it permits something. His son-in-law the Chasam Sofer seems to disagree that this is a significant difference between these authorities
 The Pri Megadim Pesicha Kolleles 1:15 questions if the Taz’s rule applies also to something learned from derashos, the thirteen hermeneutic principles, and halacha l’moshe misinai. He says that the Taz explicitly applies it to derashos, as he uses it to explain why Chazal didn’t forbid bris milah on Shabbos, even though a person might carry the knife (just like we are concerned by Shofar, Megillah, and Lulav; see Rosh Hashanah 29b). He says that the Torah explicitly permitted bris milah on Shabbos. Other Rishonim ask about bris milah and give a different answer. It doesn’t necessarily mean they disagree with the Taz’s rule, but they might just limit it to explicit verses and not derashos. However, the Teshuvos Chavos Yair § 142 disagrees with the Taz, and asks a strong question on him regarding lending to a non-Jew with interest. See Teshuvos Rabbi Akiva Eiger 2:32, who answers for the Taz
 In the above three sources, the Taz is inconsistent in his phraseology. He writes אין להם לגזור, which sounds like they don’t have the right. He writes לא רצו, saying that they wouldn’t want to. He also writes אין כח ביד חכמים, saying that they don’t have the ability. However, the later authorities seem to take on that his intent is that Chazal could, but chose not to decree against what the Torah explicitly permitted
 Beis Menachem 1:1, by Rav Mordechai Michael Yafe, brought in Teshuvos Bikkurei Shlomo Even HaEzer 4:14, by Rav Shlomo Avraham Razketa
 Teshuvos Heichal Yitzchak Even HaEzer 10:11, by Rav Yitzchak Herzog, the first Chief Rabbi of the State of Israel
 This question was presented to Rav Nesanel Fried (a 20th century Rav in Europe, brought in his Teshuvos Penei Meivin Orach Chaim 168) by Rav Yekusiel Yehuda Greenwald, in the name of his father. It was also asked by Rav Rachamim Eliyahu Chazan in his Orach Mishpat § 2 Hagahos HaTur § 11 (I’m not sure who was earlier). As an aside, Rav Greenwald happened to be the Rav of Columbus, Ohio in the early 1900’s for over forty years. He was a prolific author
 Penei Meivin loc. cit.
 It’s not clear what he means though, as the Taz addresses why Chazal didn’t forbid blowing the Shofar on a regular Rosh Hashanah (one that doesn’t fall on Shabbos), even though there’s a general decree against playing musical instruments. In that instance, the decree is due to a side concern, that one may end up fixing a broken instrument. According to the Penei Meivin, they actually should have made this decree, and it wouldn’t contradict the Taz
 Yafeh LaLev IV Choshen Mishpat § 2, by Rav Chaim Palagi’s son, Rav Rachamim Nissim Yitzchak
 In fact, the Taz himself explicitly says this regarding Shofar
 Ginzei Yosef 73:3, by Rav Yosef Schwartz
 Rabbeinu Bachaye ad. loc., based on Vayikra Rabbah 34:8 (and perhaps the Zohar in the next note)
 Zohar Chadash parshas Lech Lecha p. 42a
 Ibid, inferring this from the word על דב”ר אשר לא קדמו. The sefer Ohr Tzadikim has printed in it something he calls “Derashos Beis Yosef”, by Rav Yosef Caro. He says he found it in someone’s collection of manuscripts. It’s unclear if this was actually written by Rav Yosef Caro, but he also says this explanation on this verse (without citing the Zohar Chadash)