In Kisavo 28:7 it says, ’Yitain Hashem es oiyvecha hakamim alecha negafin lifanecha’. Hashem will deliver your enemies who come upon you, to be stricken before you. The posuk says the enemies ‘who come upon you’ will get this curse, the posuk does not simply say your enemies will get the curse. Chazal say there is a klal gadol [a big rule] that Eisav hates Yaakov. That being so, Klal Yisrael will certainly have many enemies, if their brother hates them surely everybody else will. This explains why the posuk does not simply say your enemies, who will be too plentiful to count. Only the ones who come up against you, with some definite action, will receive the curse. —Aznayim Latorah