Receiving the munn and offering the Omer
דבר אל-בני ישראל ואמרת אלהם כי-תבאו אל-הארץ אשר אני נתן לכם וקצרתם את-קצירה והבאתם את-עמר ראשית קצירכם אל הכהן: והניף את-העמר לפני יקוק לרצנכם ממחרת השבת יניפנו הכהן
Speak to the Children of Israel and say to them: When you come to the land that I give to you, and you harvest its produce, you shall bring the Omer, the first of your harvest, to the Kohen. He shall wave the Omer before Hashem, to make you desirable; the day after Pesach the Kohen shall wave it.
וספרתם לכם ממחרת השבת מיום הביאכם את-עמר התנופה שבע שבתות תמימת תהיינה: עד ממחרת השבת השביעת תספרו חמשים יום והקרבתם מנחה חדשה ליקוק
You shall count for yourselves, from the day after Pesach, from the day you brought the waved Omer, seven weeks, which shall be perfect. Until after the seventh week, count fifty days, and then offer a new flour offering to Hashem
The Omer flour offering which was brought the day after Pesach is highly unusual. An omer is literally a volume of flour, also known as a tenth of an eiphah. All other flour offerings don’t use the word omer to describe their quantity, and indeed simply say a tenth of an eiphah. Why then does this offering use the term Omer? More than that, this offering is known by name by its volume of flour. Why is it called the Omer offering? Further, there’s a mitzvah to count every day up to fifty days after Pesach. This mitzvah is called Sefiras HaOmer, literally the counting of the Omer. The whole point of the mitzvah is the anticipation of the festival of Shavuos, which culminates the fifty-day count. Why then is the mitzvah to specifically count “from the Omer”?
Another curiosity is the amazing things our Sages have to say about the Omer offering. They say that because of the Omer offering, Avraham merited to inherit the land of Canaan to his children. The Omer offering brings marital harmony between husband and wife. It saved the Jews during the days of Gidon, King Chizkiyahu, Yechezkel, and Haman. These aggrandized statements need explanation What’s so great about the Omer offering that it could have accomplished all these tremendous salvations and provided such rewards? We don’t find this with any other offering, flour or otherwise.
One explanation offered for the Omer offering is that it’s to remind us of the tremendous chessed that Hashem constantly does for us. Hashem consistently renews our crops for our sustenance, therefore it is fitting to offer to Him from our first harvest. This way we’ll remember His kindness, before we benefit from it. As said before, the explanation behind the Sefiras HaOmer, is to show our great anticipation for Shavuos. Shavuos commemorates when the Jewish people received the Torah. The whole purpose for why Hashem took us out of Egypt was so we could receive the Torah on Mount Sinai. That’s why we start counting the day after Pesach, until Shavuos. It would appear then that the mitzvah of counting doesn’t have a connection to the Omer offering. Therefore, we still have the question of why the counting is from the Omer, and not “from Pesach” or “until Shavuos”.
A possible explanation for all of these questions is based on the following Midrash: Hashem told Moshe to tell the Jewish people, that when Hashem gave us the munn, He gave the volume of an omer to each and every individual. Now, when the Jews “give Hashem” the Omer, there’s only one, and it’s made from barley. We see from here that there’s a connection between the Omer and the munn that the Jews received. Especially since other flour offerings are also the volume of an omer, yet Hashem specifically chose the Omer offering to compare to the munn. What does this signify?
For forty years in the wilderness, Hashem rained munn from the Heavens for every individual. There was exactly enough for everybody; no one received too much or too little. The munn fell for them wherever they travelled and wherever they encamped. They received it without any toil or work. This taught them and gave them crystal-clear understanding that everything comes from Hashem. It is He that sustains and nourishes all. This happened every day for forty years, to engrain this concept in their minds and hearts.
However, once they entered the land, each person went to his field and started to work. They plowed, they sowed, they harvested. They did all the farm work necessary to produce crops to consume. This everyday work could chip away at the faith they had developed in the wilderness. To counteract this natural outcome, the Jews were commanded with the mitzvah of the Omer offering. This is why they were commanded only once they entered the land. This flour offering was to be called the Omer offering, to remind them of the omer amount of munn they received in the wilderness. The time chosen to offer the Omer offering was the day that the munn stopped falling from Heaven.
This is also an additional reason for Sefiras HaOmer, the mitzvah of counting between Pesach and Shavuos. Hashem knew that a once a year offering wouldn’t be enough to maintain the faith that had been engrained in the wilderness. Therefore, Hashem added a mitzvah upon every Jew to count for seven weeks. Every day they would count with reference to the Omer offering. “Today is day one of the Omer”. “Today is day two of the Omer”. All of this was to cement in everyone’s minds that Hashem is the provider of all nourishment, and that man’s efforts aren’t the source of their food. This way, this fundamental principle will never be forgotten.
 Based on Be’er Yosef to Leviticus 23:9,10, 15,16
 See Rashi ad. loc.
 Leviticus loc. cit.
 Exodus 16:36
 For example, Leviticus 5:11
 Sefer HaChinuch § 306, as elaborated below
 Vayikra Rabbah 28:6
 Based off of Genesis 17:8-9
 The Yedei Moshe and Eitz Yosef ad. loc. explain that just like the Omer offering comes from barley, so too the Sotah offering, which itself reunites estranged husband and wife (see Numbers 5:11-31). The Eitz Yosef elaborates that just like the Omer unites the Jewish people and the Divine Presence (Zohar), so too the Sotah offering reunites husband and wife
 Based off of Judges 7:13
 Based off of Isaiah 30:32
 Based off of Ezekiel 4:9
 See Megillah 16a and Esther Rabbah 10:4
 Sefer HaChinuch § 302
 Vayikra Rabbah 28:3; Zohar III p. 96a
 Exodus 16:16
 Kiddushin 38a