יְשַׁלַּ֣ח יְהוָ֣ה ׀ בְּ֠ךָ אֶת־הַמְּאֵרָ֤ה אֶת־הַמְּהוּמָה֙ וְאֶת־הַמִּגְעֶ֔רֶת בְּכָל־מִשְׁלַ֥ח יָדְךָ֖ אֲשֶׁ֣ר תַּעֲשֶׂ֑ה עַ֣ד הִשָּֽׁמֶדְךָ֤ וְעַד־אֲבָדְךָ֙ מַהֵ֔ר מִפְּנֵ֛י רֹ֥עַ מַֽעֲלָלֶ֖יךָ אֲשֶׁ֥ר עֲזַבְתָּֽנִי׃
네가 악을 행하여 그를 잊으므로 네 손으로 하는 모든 일에 여호와께서 저주와 공구와 견책을 내리사 망하여 속히 파멸케 하실 것이며
Or HaChaim
Another factor we have to keep in mind is that the curse itself- something we normally perceive as abstact becomes concretised- and the destructive force it represents assumes the very "name" of the curse itself. We know this from Deut. 28,20 where G'd threatens to send the מארה, or the מגערת, "the curse or the rebuke." These are names for categories of destructive forces. The word קללה describes the category of curse resulting from the commission of a serious sin, whereas the word זעם describes the destructive force created by relatively minor sins. To sum up, when Bileam wished to curse a nation he chose the time when they were all guilty at least of relatively minor sins. Inasmuch as most people are guilty of some sins almost all of the time Bileam could expect his words to be effective. He employed his sorcery to determine if at that time most of the Israelites still suffered from sins which they had not repented or for which they had not as yet been punished. Having examined the status of the Jewish people on that basis, he came to the regretful conclusion of מה אקב, "how can I be expected to make a curse effective" seeing that the spiritually negative forces had not been able to establish their hold on any part of the collective Jewish soul, their holy roots? The Israelites were so innocent at the time that Bileam was not able to activate sins they had committed to act as a curse against them.
Or HaChaim
והיה אם לא תשמע, "It will be if you do not hearken, etc." The Torah made it plain here that unless we fulfil all three aspects of Judasim i.e. Torah study, scrupulous observance of the negative commandments, and the carrying out of positive commandments, some or all of the consequences described forthwith will occur. Learning Torah and not observing the negative commandments does not protect us. Observing both negative and positive commandments but neglecting the study of Torah will still result in the curses of the following verses being fulfilled. Non-observance of each of these three groups of Torah laws will attract its own kind of curses. The Torah commences by describing the punishments in store for the Jewish people if they fail to study Torah. .ארור אתה בעיר, "you will be cursed in the city;" this verse until the words ואבדך מהר, "and you will quickly perish" and the end of verse 20 are a row of escalating curses which are retribution for abandoning Torah, i.e. abandoning Torah study. When one abandons study of the Torah it is viewed as if one had abandoned G'd Himself. This is why this paragraph concludes with the words אשר עזבתני, "for you have abandoned Me."
Ramban
In the blessings he mentioned first the fruit of thy body87Above, Verse 4. and afterwards thy basket and thy kneading-trough88Ibid., Verse 5. for the fruit of the body is the best and most beloved, but in the curses he delayed it [mentioning first thy basket and thy kneading-trough in Verse 17, and the fruit of thy body in Verse 18] because the punishment extends first to a man’s possessions,89Vayikra Rabbah 17:4: “The Merciful One does not smite human life first.” and, if he does not repent, it reaches the fruit of his body. Similarly, in the blessings he mentioned first the smiting of the enemies90Above, Verse 7. before the blessing in thy barns, and in all that thou puttest thy hand unto,91Ibid., Verse 8. for triumph over the enemy is the honor and necessity for them in the conquest of the lands, and their dwelling safely among the peoples. And in the curses he mentioned first the diminishing in all that thou puttest thy hand unto to do92Further, Verse 20. and delayed their being smitten before the enemies,93Ibid., Verse 25. for this is the punishment that would reach them afterwards — and in the end they would be exiled.94Ibid., Verse 68.