The passuk states “לא יבא עמוני ומואבי בקהל ה’…” which Onkelos translates as “Do not purify Amon and Moav to enter into the assembly of Hashem; even the 10th generation do not purify them to enter into the assembly of Hashem, forever.” Why does Onkelos translate יבא as “purify them to enter in,” what purification is there entering into the assembly? The Nesina LaGer adds that the Mishnah uses this lashon as well: mamzeirim are able to become purified… Also it states in Malachi וישב מצרף ומטהר כסף וטהר את בני לוי… and He will sit and refine and purify silver, and purify the Bnei Levi and refine them as gold and as silver. The Metzudas Dovid explains: just as one who refines gold and silver removes the bad parts from the good parts, so too Hashem will separate the good Kohanim from ones who are not good. The Malbim adds He will separate the Kohanim from the Levi’im, to be able to do avodah in the Bais HaMikdosh. Onkelos translates “purify them to enter in” which refers to preparing and cleansing the nations to enable them to be fitting to enter into the assembly.
The passuk states Amon and Moav cannot enter into the assembly because: “על דבר אשר לא קדמו אתכם בלחם ובמים…” “For not coming towards you with bread and water on the road when you went out of Mitzrayim” andואשר שכר עליך את בלעם בן בעור מפתור ארם נהרים לקללך “and for that which you hired Bilam the son of Be’or from Pesor, Aram Naharayim, to curse you.” This seems that for not coming towards us to give us bread and water or for hiring Bilam to curse us is why Amon and Moav are not allowed into the kahal. The Kli Yakar is bothered, why is their punishment so harsh that they are distanced forever?
The Ramban explains differently, Amon and Moav were brothers who owed tremendous appreciation to Avraham for his kindness, for saving their parents from being killed in the war of the 4 and 5 kings, and for being saved from the destruction of Sedom in Avraham’s merit. They had an obligation to show appreciation and do good to Yisrael, yet Amon did not come towards Yisrael to give or even sell them any bread or water, and Moav hired Bilam to curse Yisrael. The passuk states one reason about Amon and the other about Moav. Amon is mentioned first because they were worse, even the Bnei Eisav and Moavim took bread and water outside their boundary whereas Amon did not. Since both Amon and Moav did not feel the obligation of appreciation they are unworthy of purifying themselves to join the kahal.
The Chovos Halevavos says one reason we don’t notice Hashem’s kindness and good in the world is because we take things for granted. We feel that we are owed the good which we receive and deserve it. He brings a mashal with two scenarios: a child who was found in the desert and was clothed, fed, and raised by someone and an adult who was captured and someone bailed him out and freed him and helped him from suffering to freedom. Although the child had more good and kindness done for him over the years, he becomes accustomed and takes for granted of all the good done for him. The adult however is knowledgeable, and is aware to recognize the kindness done with him. He will in turn express his appreciation much more.
May Hashem help us recognize His constant goodness and kindness and express appreciation!