Or HaChaim on Genesis 34:13/אור החיים על בראשית ל״ד:י״ג

1 ויענו בני יעקב, The sons of Jacob replied, etc. We have to understand exactly what wisdom Onkelos attributes to Jacob's sons when he translates the word במרמה as "with wisdom" instead of as "with guile." At first glance it appears that the sons of Jacob simply meant to deceive Chamor and Shechem. Besides, what is meant by וידברו אשר טמא את דינה?

2Actually, the cleverness of the sons when they answered Chamor במרמה consisted in that they answered him in such a way that their proposal seemed extremely plausible. Shechem and Chamor did not feel that they needed to be on guard against reprisals. The brothers lulled Chamor into a false sense of security by the very fact that they threatened to take some action if their proposal was not accepted; they thus made him believe that if the town accepted the proposal of mass circumcision the whole chapter of the rape would be closed. The word וידברו, a term describing harsh words, indicates that the brothers first harped on the fact that their sister had been sullied. By doing so they ensured that Chamor and Shechem could not accuse them of giving conflicting signals, i.e. suggesting intermarriage while at the same time condemning the people of Shechem for their immoral behaviour.

3They then continued speaking in a friendly tone, saying לא נוכל, "we cannot intermarry, etc.," suggesting that they would like to but could not under existing conditions, i.e. while the males of Shechem remained uncircumcised. When they described the condition of the local inhabitants as אשר יש לו ערלה, they meant that whereas the local people were not required to circumcise themselves, it was not enough for Chamor or Chamor and Shechem alone to perform circumcision on themselves. In fact, even if they were to circumcise themselves as a voluntary act they would still be regarded by Jews as ערלים, seeing they did not fulfil a commandment by removing their foreskin.

4They would consider intermarriage with the people of Shechem and the merging of the two clans only on condition that the entire male population of Shechem would be circumcised. They emphasised this in order to forestall an offer by Chamor and Shechem to circumcise only themselves and their future male offspring. The brother's entire purpose was to facilitate killing the people of Shechem with a minimum of resistance on the part of the latter. They worded their conditions so that they would not be suspected of merely tricking the people of Shechem.