Halakhah su Levitico 23:10

When we investigate the Torah’s year, we find written “This month shall be for you the beginning of months” (Exodus 12:2), so it is first of the months of the year. It is also written “This day you depart, in the month of ripening” (ibid. 13:4), and “Observe the month of ripening” (Deuteronomy 16:1). The explanation is that Israel counts by lunar months, and the month in which the barley ripens in the Land of Israel is the first of the year’s months. The beginning of that month is the beginning of the year, whether the equinox has passed or not. However, in order to perform the waving of the Omer ⁷⁸ The Omer waving took place on the second day of Passover, the sixteenth of Nisan (Leviticus 23:10–11). the court should ensure that Passover will occur when the barley has ripened.⁷⁹ There are exceptions to this requirement. See Ibn Ezra’s commentary to Exodus 12:2 and to Deuteronomy 15:1. Most years the ripening coincides with the equinox, but sometimes they are separated slightly because of an abundance of rain or because of drought.

The commandment of the sacrifice of the omer of barley: That we offer on the second day of Pesach, beyond the additional offering of the rest of the days of Pesach, a one-year old sheep for a burnt-offering and one omer of barley, that is called the omer of waving - as it is stated (Leviticus 23:10-11), "When you come to the land, etc., you shall bring the omer, the beginning of your harvest, etc. And he shall wave the omer in front of the Lord from the morrow of the Shabbat." And Onkelos translates, "after the holiday" - meaning to say, on the second day of Pesach. As behold, it is referring to Pesach in the section before this. And it is stated there (Leviticus 23:12), "And you shall make on the day of your waving the omer an unblemished one-year old sheep, etc." And this sacrifice of the omer is called the offering of the first fruits. And it is a hint to this when He may He be blessed, says (Leviticus 2:14), "And if you shall bring an offering of the first-fruits to the Lord, new roasted with fire, etc." And the language of Mekhilta d'Rabbi Yishmael 22:24 is "Each and every 'if' in the Torah is optional, etc. except for three that are obligatory and this is one of them." And they said there, "You say it is an obligation or is it only optional? [Hence] we learn to say, 'you shall offer the offering of your first fruits' - [it is] an obligation and not optional. And the matter of the offering is thus (Menachot 63b): That they would bring three seah of barley, and they would take out one issaron from all of it, which they would sift with thirteen sieves. And the rest would be redeemed and eaten by any person. And it is liable for the hallah-tithe but exempted from the [other] tithes. And we take this issaron of fine barley flour and we mix it with a log of oil and place a handful of frankincense upon it - like the other meal-offerings. And the priest waves it in the East - he extends [it] and brings [it back], raises [it] and lowers [it] - and presents it across from the point of the southwest corner, like the other meal offerings. And he takes a handful and incinerates [it], and the rest is eaten by the priests, like the remainders of all of the meal-offerings (Menachot 67b).