Parashas Shemos
וְאַחַ֗ר בָּ֚אוּ מֹשֶׁ֣ה וְאַהֲרֹ֔ן וַיֹּאמְר֖וּ אֶל־פַּרְעֹ֑ה כֹּֽה־אָמַ֤ר יְהֹוָה֙ אֱלֹהֵ֣י יִשְׂרָאֵ֔ל שַׁלַּח֙ אֶת־עַמִּ֔י וְיָחֹ֥גּוּ לִ֖י בַּמִּדְבָּֽר׃
Afterward Moses and Aaron went and said to Pharaoh, “Thus says the ETERNAL, the God of Israel: Let My people go that they may celebrate a festival for Me in the wilderness.”
Torah Temimah points to Rav Pappa / Abaye — TT (verified).
ויחגו לי במדבר — \ldots ממאי דהאי ויחגו לי זביחה היא.
English: “That they may celebrate (yachogu) to Me in the wilderness” — \ldots from where [do we know] that this “yachogu” means sacrifice?
Custom
Chazal establish that the demand to “celebrate” already implies sacrificial worship.