וּשְׂמַחְתֶּ֗ם לִפְנֵי֮ יְהוָ֣ה אֱלֹֽהֵיכֶם֒ אַתֶּ֗ם וּבְנֵיכֶם֙ וּבְנֹ֣תֵיכֶ֔ם וְעַבְדֵיכֶ֖ם וְאַמְהֹתֵיכֶ֑ם וְהַלֵּוִי֙ אֲשֶׁ֣ר בְּשַֽׁעֲרֵיכֶ֔ם כִּ֣י אֵ֥ין ל֛וֹ חֵ֥לֶק וְנַחֲלָ֖ה אִתְּכֶֽם׃
And ye shall rejoice before the LORD your God, ye, and your sons, and your daughters, and your men-servants, and your maid-servants, and the Levite that is within your gates, forasmuch as he hath no portion nor inheritance with you.
Sifrei Devarim
(Devarim 12:12) "And you shall rejoice": It is written here "rejoicing," and, elsewhere (27:7) "rejoicing." Just as the "rejoicing" there is with peace-offerings, so, the "rejoicing" here.