The traditional Passover song "Dayenu" literally means "it would have been enough" and lists the 15 gifts and miracles (like parting the Red Sea) bestowed upon the Jewish people by God in the Book of Exodus. The idea that each blessing would be enough on its own, even without further or more profound blessings, is a central theme during the holiday.
"Dayenu" is sung throughout the diaspora during the seder, but Sephardic Jews from Iran and Afghanistan have a particularly lively custom in which they whip each other with oversize scallions. Before the song begins, each seder participant stands, takes a scallion and starts whacking the other members of the feast. In some families, one scallion is passed around the table while each person takes a turn whipping. There is some debate about where the custom originates. Many believe it is a way to mimic the whips of slave drivers in Egypt. But others say it's a reference to Bamidbar 11:5-6, a passage that describes the Israelites' longing for Egyptian onions while eating manna during their 40 years wandering in the desert. Seder participants whip one other as a way to scold one another for desiring any aspect of their lives of enslavement.