The Pesach Haggadah states: “What does the wicked son say? ‘What is this service to you,’ this implies ‘to you’ and not ‘to himself’. Since he has excluded himself, he has thus denied the existence of Hashem. You should therefore likewise blunt his teeth (scold him) and reply to him, ‘Because of this did Hashem do this for me when I left Egypt.’”
Maran Rabbeinu Ovadia Yosef zt”l recounts that once Hagaon Harav Tzvi Yechezkel Michelzon was asked why the author of the Haggadah was so bothered by the wicked son’s question of “What is this service to you” so much so that he says that one should blacken his teeth if the Torah specifically states that when the wicked son asks this question, he should be replied to calmly and respectfully, as the verse states, “And it shall be when your sons will tell you, ‘What is this service to you?’ And you shall tell them, ‘This is a Pesach feast-offering for Hashem, for he had skipped over the houses of the Jewish nation when he smote Egypt but He saved our households.’” If this is indeed the case, why has the author of the Haggadah instructed us to deal so harshly with the son who poses this question?
Harav Michelzon zt”l replied that if this son were the only wicked individual in the entire city or vicinity where everyone else is righteous and upstanding, he would be ashamed to ask “What is this service to you” as though he has no connection to the matter at all. He will certainly not have the audacity to mock the tradition of the entire city, for if he would, the entire city would scorn him for speaking against them in such an audacious, arrogant, and disparaging manner.
In such a scenario where the wicked son is alone, he certainly deserves to be replied to harshly since he is attempting to harm the community’s belief in Hashem and convince them of his foolish ideas.
However, if the amount of wicked people grows like we are unfortunately encountering in our generation and the wicked individuals become the majority of the city’s population, they will have no hindrance and they will be brazen enough to speak whatever is on their mind and they will scream, “What is this service to you?”
Thus, the Torah, whose paths are pleasant and peaceful, states, “When your children (plural) say to you, ‘What is this service to you?’” you shall reply, “And you shall say (softly) this is a Pesach feast-offering for Hashem.” This is because it is forbidden to instigate the wicked when they are in their glory and in control.
Thus, since in the context of the Haggadah there is only one wicked son and he is even foolish enough to jump and speak first by saying, “What is this service to you,” we must act quickly and castigate him! (See Chazon Ovadia-Haggadah Shel Pesach, page 218)
