By Rabbi Yair Hoffman
The day after Pesach and Sukkos is called Isru Chag, which literally means “bind or connect the festival.” The Gemorah (Sukkah 45b) tells us in the name of Rabbi Yochanan in the name Rabbi Yochanan HaMekusi:
“Whomsoever celebrates Isru Chag with eating and drinking, the Pasuk considers it as if he had built a Mizbeach and offered korbanos upon it.” The Gemorah is actually making a drasha on the verse in Tehillim (118:27), where it states, “Tie the festival offering to the corners of the Mizbeach with strings.”
Chazal darshen that this means to continue the joy of the Yom Tov onward to the next day. In this statement it is clear that the sages wish us to continue the Yom Tov, and to do so in a festive spirit including food and drink. The Arizal explains that there are still sparks of kedusha from the Yom Tov that are left over. These sparks should be channeled properly. The concept is cited in the Ramah (OC 429:2). The custom in Ashkenazic circles is to greet one another with a wish of a “Gezunter summer – a healthy summer.”
We see from the Sdei Chemed (Aleph #154) an additional theme in the notion of Isru Chag. He writes that the practice originated in Eretz Yisroel because the Bnei Torah of Eretz Yisroel were concerned that the gentiles were feeling that the Jews were not united. Those outside of Eretz Yisroel observed two days of Yom Tov. Those within Eretz Yisroel observed one day. Gentiles perceiving this would erroneously think that the Jews were divided and alienated from one another. They therefore began the observance of Isru Chag to demonstrate the unity of the Jewish people.
This then is an additional theme that we can focus upon on Isru Chag. The extension of Achdus, friendship and unity, will help continue the message of the Yomim Tovim. The custom is also not to fast during this time (See Magain Avrohom 425:8).
One final lesson. Rav Elyashiv zatzal writes (Divrei Agaddah p. 458) that on Isru Chag everyone should make sure that the infusion of spirituality that he or she had received during the Yom Tov continue to be tied to the rest of the year. This is the obligation of Isru Chag – the “binding of the holiday.”