By: Rabbi Ari Enkin
You’re just not going to believe this one…..
From the Sefer Kushiot #11
Q. Why is there a custom for those gathered at a wedding to slap the designated witnesses as the kiddushin is taking place?
A. It derives from the fact that the laws of marriage and kinyanim (acquisitions) are derived from the words “kicha, kicha” (meaning “to take” or “to acquire”), that appear in the context of Avraham purchasing the Machpela cave from Ephron. Since “kicha” has the same gematria as “ketata” (fighting) and we are taught that there is no marriage that does not include some fights and arguments, the witnesses are slapped by everyone present in the hope that any fighting that might have been decreed upon the couple be discharged right then and there through the slapping of the witnesses.
Another version of the Sefer Kushiot manuscript has it that the two witnesses are simply to slap one another without the “participation” of everyone gathered. Additionally, in a footnote on this entry in the Rabbi Yakov Stahl edition of Sefer Kushiot there is a closely related custom cited for the groom to slap the bride under the chuppa until her tooth falls out [!]. This, again, in order for the slapping to discharge any fighting that might have been decreed upon the couple. With this slap, the kiddushin was said to be complete.