Positive commandment · Mitzvat Aseh #44 of 613
Sacrifice of the omer of barley
להקריב מנחת העומר ממחרת יום ראשון של פסח עם כבש אחד
The verse · Vayikra 23:10
דַּבֵּר אֶל־בְּנֵי יִשְׂרָאֵל וְאָמַרְתָּ אֲלֵהֶם כִּי־תָבֹאוּ אֶל־הָאָרֶץ אֲשֶׁר אֲנִי נֹתֵן לָכֶם וּקְצַרְתֶּם אֶת־קְצִירָהּ וַהֲבֵאתֶם אֶת־עֹמֶר רֵאשִׁית קְצִירְכֶם אֶל־הַכֹּהֵן
“Speak to the children of Yisra᾽el, and say to them, When you are come to the land which I give to you, and shall reap its harvest, then you shall bring an ῾omer of the firstfruits of your harvest to the priest:”
The Rambam’s words
To bring the meal offering of the omer on the day after the first day of Pesach together with a single lamb, as [Leviticus 23:10] states: "And you shall bring the omer...."
להקריב מנחת העומר ממחרת יום ראשון של פסח עם כבש אחד, שנאמר: "וַהֲבֵאתֶם אֵת עֹמֶר רֵאשִׁית קְצִירְכֶם אֶל הַכֹּהֵן" (ויקרא כג, י).
Why · Sefer HaChinuch #302
Sacrifice of the omer of barley
“It is from the roots of the commandment [that it is] in order that we contemplate, through [this] deed, the great kindness that G-d, blessed be He, does for His creatures, to renew the grain each year for [our] nourishment.”
Who & when
“And this commandment is practiced at the time of the [Temple] with males.”
Where in the Mishneh Torah
Hilchot Daily Offerings and Additional Offerings הלכות תמידים ומוספין