Receiving the munn and offering the Omer[1]
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[2]; the day after Pesach[2] 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[3]
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[4]. All other flour offerings don’t use the word omer to describe their quantity, and indeed simply say a tenth of an eiphah[5]. 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[6], which culminates the fifty-day count. Why then is the mitzvah to specifically count “from the Omer”?