פּירוש אויף בראשית 34:25

שני בני יעקב TWO OF THE SONS OF JACOB — They were his sons (the sons of Jacob, a wise and clever man), but they acted as any man named Simeon and Levi would do — as other people would do who were not his sons — for they did not take counsel with him (Genesis Rabbah 80:10).

ויהי ביום השלישי בהיותם כואבים, “It was on the third day when they are in pain:” they were all in pain and regretted having agreed to undergo circumcision: when Yaakov’s sons heard about this and they also heard that Chamor and Sh’chem had altered the conditions they had agreed to with them, i.e. that no one was allowed to leave the town before he had undergone circumcision, plus their having presented the whole agreement as due to enhancing the honour of the people of Sh’chem instead of in response to an ultimatum by the sons of Yaakov, plus the fact that they boasted that henceforth the herds and flocks of Yaakov’s family would (verse 23) be theirs, they decided to attack the city’s inhabitants. The reason they had waited until the third day was that it took the people of Sh’chem until that day to complete the process of circumcising all the men and boys. On that day those who had been circumcised on the first day were still suffering from pains and relatively weak. This is why the Torah writes: ויבואו על הער בטח, “they came into the city unopposed, without having to worry.” This is also how Onkelos translated it. A different exegesis: Shimon and Levi entered the town while the inhabitants were sitting, feeling themselves secure.

ויהי ביום השלישי בהייותם כואבים, “it was on the third day (after circumcision) when they were all in pain, etc.” it is difficult to understand why the brothers had insisted that all these people circumcise themselves when they had meant to kill them anyways. Why did they have to resort to such deceit? Our verse may provide the answer by reporting that on that day the men of Sh’chem regretted having circumcised themselves. It was on account of that Shimon and Levi killed them. There had been no intent to kill them when they demanded that they circumcise themselves if they wanted to become members of the clan of Semites. Their act of circumcision was perceived by them as an initiation rite. Also, there is no reason to assume that they should have been in greater pain on the third day than on the previous two days. In fact, it is likely that they had not been able to circumcise themselves all on a single day, and the third day that the Torah speaks of was the day when these circumcisions were completed. This is why Shimon and Levi did not take their swords until the third day.