Positive commandment · Mitzvat Aseh #144 of 613
To give the first portion of the fleece to a priest
ליתן ראשית הגז לכוהן
The verse · Devarim 18:4
רֵאשִׁית דְּגָנְךָ תִּירֹשְׁךָ וְיִצְהָרֶךָ וְרֵאשִׁית גֵּז צֹאנְךָ תִּתֶּן־לוֹ
“The firstfruit also of thy corn, of thy wine, and of thy oil, and the first of the fleece of thy sheep, shalt thou give him.”
The Rambam’s words
To give the first portion of the fleece to a priest, as [Deuteronomy 18:4] states: "Give him the first portion of the shearing of your sheep."
ליתן ראשית הגז לכוהן, שנאמר: "וראשית גז צאנך--תיתן לו" (דברים יח,ד).
Why · Sefer HaChinuch #508
To give the first shearing to the priest
“It is from the roots of the commandment [that] since G-d, may He be blessed, chose the tribe of Levi from among his brothers for His service in the Temple always, therefore it was from His kindness to them to give them their sustenance in an honorable way.”
Who & when
“And this commandment is practiced by males and females, Israelites and Levites, whether in front of the [Temple] or not in front of the [Temple].”
Where in the Mishneh Torah
Hilchot First Fruits and other Gifts to Priests Outside the Sanctuary הלכות ביכורים ושאר מתנות כהונה שבגבולין