ציטירנדיקער פּירוש אויף אסתר 6:4

אשר יטמא לו, “whereby he may become ritually unclean;” the word לו in this verse means בשבילו, “on its account,” on account of the creeping animal. It is parallel to Exodus 1,10, where Pharaoh exerted his people to outsmart the Israelites since he could not outnumber them and said: הבה נתחכמה לו, “let us instead try to be smarter than it,” i.e. “on account of its numerical superiority.” It is also similar to Esther 6,4: אשר הכין לו, “which he had prepared on his account.” (On Mordechai’s account, in order to hang him from that gallows). Our author cites more parallels.