Or HaChaim on Deuteronomy 27:26/אור החיים על דברים כ״ז:כ״ו

1 ארור אשר לא יקים את דברי התורה הזאת, "Accursed is one who does not uphold the words of this Torah, etc." This verse includes both what is spelled out, i.e. the person who fails to observe the commandments mentioned in this paragraph and to thereby undermine the character-building effects of Torah observance, as well as all the other commandments not listed in this paragraph. Our sages in Sotah 37 concentrate on the wording here, i.e. אשר לא יקים…לעשות. Why was it not sufficient for the Torah merely to write לעשות, "to do?" They say that if the Torah had only written the words לא יקים or לעשות, no Israelite would have been able to face G'd. After all, if one does not own a field, for instance, how can one fulfil all the commandments that a farmer has to fulfil? Or, if a person did not own a slave, how could he be expected to treat the slave in accordance with the duties that the Torah imposes on the owner of such a slave? This is why the Torah adds the words לעשות in addition to writing the word להקים, "to uphold," to tell us that unless one has the opportunity to uphold, i.e. to fulfil the commandments of the Torah, one is not subject to the curse pronounced by the Torah through the Levites in this paragraph. It is our duty to make up our minds that we will carry out the commandments when the opportunity arises to do so.