לֹֽא־יָבֹ֧א עַמּוֹנִ֛י וּמוֹאָבִ֖י בִּקְהַ֣ל יְהוָ֑ה גַּ֚ם דּ֣וֹר עֲשִׂירִ֔י לֹא־יָבֹ֥א לָהֶ֛ם בִּקְהַ֥ל יְהוָ֖ה עַד־עוֹלָֽם׃
Nie wnijdzie Ammonita i Moabita do zgromadzenia Wiekuistego; nawet dziesiąte pokolenie ich nie wnijdzie do zgromadzenia Wiekuistego na wieki;
Rashi
לא יבא עמוני AN AMONITE [OR MOABITE] SHALL NOT COME [INTO THE ASSEMBLY OF THE LORD] — i.e. he shall not marry an Israelite woman (Yevamot 77b).
Chizkuni
לא יבא עמוני ומואבי בקהל ה, “male members of the Ammonite or Moabite peoples must not marry Jewish women. This rule follows the rule about bastard because marriage with both is forbidden forever.
Or HaChaim
לא יבא עמוני ומואבי בקהל השם, "Neither an Ammonite nor a Moabite may become members of the Jewish people, etc." The reason which the Torah gives for denying the male members of these tribes the right to convert to Judaism, i.e. that they did not come forward with bread and water to assist the Israelites when the latter came out of Egypt is hard to understand. Does not the Torah itself testify in Deut. 2,29: "as did the members of the tribe of Esau and the Moabites?" The reference is to both of these nations having sold provisions to the Israelites at the time. Rashi explains the apparent contradiction as 1) the verse in 2,29 referring to the Israelites' offer to buy food in return for money (2,28). 2) What is written here refers to the fact that they hired Bileam to curse the Jewish people and to lead it into sin at the end of the 40 years trek through the desert whereas what is written earlier refers to what transpired in the first year of the Israelites' wanderings. Perhaps the word על דבר is meant to alert us that what they did with Bileam would have sufficed to exclude them forever as members of the Jewish people. The word קדמו means they should have come forward on their own account offering bread and water as gifts. This would have been only small recompense for all which our forefather Abraham had done for them. Instead of repaying good with good they had repaid good with evil. The plain meaning of the words לא קדמו אתכם is that they did nothing for your benefit.