Isru Chag

The day after Pesach, Shavuot, and Sukkot is known as "Isru Chag," and is treated with some degree of sanctity. The name "Isru Chag," which means "wrapping up the holiday," originates in Tehillim where it says "bind the festival offering (’Isru Chag’) to the corners of the altar.”[1] Tachanun is not recited on Isru Chag, and it is also forbidden to fast.[2] Many have the custom to wear their Yom Tov clothes on Isru Chag.[3] There were communities in the past that treated Isru Chag like Chol Hamoed.

Isru Chag is viewed as the day that bridges the sanctity of the holiday that just concluded with the return-to-routine and mundane nature of the days that follow. As such, it is a quasi-holiday that possesses a festive flavor.[4] The Arizal teaches that the holiness of the holiday can be felt on Isru Chag, as well.[5] There are no work-related restrictions on Isru Chag.

Although there are no specific mitzvot that must be observed on Isru Chag, one is encouraged to indulge in more elaborate meals than usual. Our sages teach that one who honors Isru Chag by eating and drinking in a festive manner is considered to have built an altar and offered a sacrifice.[6] Isru Chag also allows for those who live in Israel to celebrate the day with some festivity together with those who live in the Diaspora (who observe yom tov sheini).[7] In fact, the Sdei Chemed writes that the Jews of Eretz Yisrael were concerned that non-Jews believed that the Jewish people were a divided nation considering that those who lived in Eretz Yisrael observed one day of Yom Tov while those who lived in the Diaspora observed two days of Yom Tov! Hence, Isru Chag essentially started as a celebration of the unity of the Jewish people.[8]Isru Chag also recalls that the pilgrims in ancient times would return to their homes with renewed excitement and inspiration after having celebrated the holiday in Jerusalem.[9] 

The days following Shavuot are especially festive. This is because in the era of the Beit Hamikdash, those who were unable to bring the Shavuot offering were able to do so anytime during the six days that followed, namely, up until the twelfth of Sivan. As such, tachanun is not recited during this entire period.[10] So too, according to some authorities, if one forgot to recite the shehecheyanu blessing on Shavuot, it may be recited during these six days. Common custom, however, is not like this view.

[1] Tehillim 118:27.

[2] Magen Avraham 425:8.

[3] Zohar Chadash, Pinchas 231.

[4] Rivevot Ephraim 3:442.

[5] Rema, OC 429:2; Torah Lishma 140.

[6] Sukka 45b, Rema, OC 429:2.

[7] Piskei Teshuvot 429:6. See also Piskei Teshuvot 496 footnote 20.

[8] Sdei Chemed, Alef 154.

[9] Piskei Teshuvot 429:6.

[10] Chagiga 17a; OC 131:7; Mo'ed Lekol Chai 8:43; Shulchan Aruch Harav, OC 494:20.