Omer

The word "omer" originally means a sheaf of barley, brought to the Temple on the day after the first day of Passover. The Torah turns it into a commandment: "you shall count off seven weeks, they must be complete," fifty days in all, until the day after the seventh week (Leviticus 23:15-16; see also Deuteronomy 16:9). The count links the Exodus from Egypt to the giving of the Torah, celebrated on Shavuot.

The Shulchan Arukh (Orach Chayim 489:1) says the count begins on the second night of Passover, after the evening prayer. Each evening, standing and after reciting the blessing, one counts the days and then the weeks, up to day 49. Day 33 is called Lag BaOmer (lamed-gimel is 33). It falls on the 18th of Iyar.

1A season of partial mourning: what the texts say

The Shulchan Arukh (Orach Chayim 493:1) records the custom not to marry between Passover and Shavuot "until Lag BaOmer," because during that time the students of Rabbi Akiva died. It states that engagements (erusin) are fine, and that someone who married anyway is not penalized. The gloss of the Rema adds that from Lag BaOmer on, everything is permitted. So this is a custom, not a prohibition from the Torah.

The same chapter (493:2) mentions the custom of not cutting one's hair until Lag BaOmer. Rabbi Yosef Karo's text waits until the morning of day 34 (unless day 33 is a Friday), while the Rema, for the Ashkenazi countries, allows a haircut on day 33 itself, a bit of rejoicing, and no Tachanun. The Rema also notes (493:3) that in many places the mourning period is counted differently, for example until Rosh Chodesh Iyar, and that a single town should not mix customs.

2How communities differ

• Families who follow the text of Rabbi Yosef Karo (many Sephardic and Mizrahi families, depending on your community's custom): the mourning runs until Lag BaOmer and, for haircuts, until the morning after.
• Families who follow the Rema's gloss (a frequent Ashkenazi custom): rejoicing begins on day 33, and weddings resume from Lag BaOmer on.
• Other ways of dividing the period: some communities place the mourning on a different stretch of the 49 days, as the Rema himself notes. Ask your rabbi which calendar your family follows.
• Secular Israelis: Lag BaOmer is mostly a popular holiday (bonfires, outings). Many families do not keep the Omer restrictions, but some still pick a date after Lag BaOmer to accommodate observant guests.

3What it means for an invitation

A wedding, bar mitzvah or other simcha that falls between Passover and Shavuot calls for checking the date early: observant guests, the caterer and the musicians should not find out late. Tov flags Omer days for the host, but your family's rabbi decides which custom applies.

Engagements are permitted according to the Shulchan Arukh (493:1); for music and dancing, customs vary from family to family. A date after Lag BaOmer is the one many families prefer, depending on their community's custom.