The Minchah-offering of the Omer
Requires Beit HaMikdash
VaYikra 23:10 Speak to Benei Yisrael and say to them; when you come into the land that I give to you and you reap its harvest, you shall bring an omer of the first fruits of your harvest to the Kohen.
We are commanded to offer a mincha-offering of barley on the 16th day of Nisan, and with it a he-lamb of the first year without blemish for a olah-offering. This mincha-offering is called "the Offering of the Firstfruits", and this is referred to in VaYikra 2:14.
The Mechilta says,
"Every if in the Torah implies an option, except in three cases where it is used in connection with an obligation; one of these is: 'And if you bring a mincha-offering of firstfruits.' You maintain this to be an obligation? Perhaps it is merely permissive. Scripture therefore says, You shall bring for the mincha-offering of your firstfruits, etc. - showing that it is obligatory and not permissive.' (Shemot 20:22, Mechilta).
Why does the Torah command us to offer a omer of the firstfruits on the Pesach? Because Pesach is the season when judgment is passed with respect to grain, and (it is as if) the Holy One, Baruch Hu, had said, "Offer before Me the first omer of grain on Pesach, so that your produce in the fields may be blessed" (Rosh Hashanah 16a).
The ceremony observed at the bring of the mincha-offering of the Omer is described in the Mishnah:
"The messengers of the Court (i.e. of the Great Sanhedrin) used to go out on the day before the Festival (of Pesach) and tie the unreaped corn in bunches to make it the easier to reap. All the inhabitants of the towns near b assembled there, so that it might be reaped with much pomp.
When it grew dark one called out, 'Has the sun set?' and they answered, 'Yes!'
'Has the sun set?' and they answered 'Yes!'
'Shall I reap?' and they answered, 'Reap!'
They reaped it, put it into the baskets, and brought it to the Temple Court. They used to beat it with reeds or stems of plants, that the grains should nlot be crushed; then they put it into a hollow tube that was perforated, so that the fire might take hold of all of it. They spread it out in the Temple Court so that the wind might blow over it. They put it into a grist-mill and took out of it a tenth (of an efah of flour), which was sifted through thirteen sieves. Then they came to the tenth, put in oil and its frankincense, poured in the oil, mingled it, waved it, and brought it near (to the Altar), took from it the handful, and burnt it; and the residue was eaten by the Kohanim." (Men. 65a, 66a; 67b).