Positive commandment · Mitzvat Aseh #196 of 613
To give a severance gift to a Hebrew servant
להעניק לעבד עברי
The verse · Devarim 15:14
הַעֲנֵיק תַּעֲנִיק לוֹ מִצֹּאנְךָ וּמִגׇּרְנְךָ וּמִיִּקְבֶךָ אֲשֶׁר בֵּרַכְךָ ה׳ אֱלֹהֶיךָ תִּתֶּן־לוֹ
“thou shalt furnish him liberally out of thy flock, and out of thy threshing floor, and out of thy winepress: of that with which the Lord thy God has blessed thee thou shalt give him.”
The Rambam’s words
To give a severance gift to a Hebrew servant, as [Deuteronomy 15:14] states: "You shall surely give him gifts...." Similarly, [this gift is given] to a Hebrew maidservant.
להעניק לעבד עברי, שנאמר: "הענק תעניק, לו" (דברים טו,יד); וכן אמה עברייה.
Why · Sefer HaChinuch #482
To endow him upon his leaving to freedom
“It is from the roots of the commandment [that it is] in order that we acquire for our souls virtuous, dear and beautiful traits; [such that] with a dear and virtuous soul, we will merit the good — and the good G-d wants to do good for His people.”
Who & when
“And this commandment is practiced by males and females at the time of the [Temple], as the law of a Hebrew slave is only practiced at the time that the Jubilee is practiced, as I have written in what preceded (Sefer HaChinukh 42).”
Where in the Mishneh Torah
Hilchot Slaves הלכות עבדים