"And they shall not appear before Me empty" (Exodus 23:15): with animal sacrifices. Or perhaps only with birds and meal offerings? It is a matter of reasoning: a festival offering is stated for the common person, and an appearance offering is stated for the Most High. Just as the festival offering stated for the common person is animal sacrifices, so the appearance offering stated for the Most High is animal sacrifices. And what animal sacrifices? Burnt offerings. Or perhaps only peace offerings? It is a matter of reasoning: a festival offering is stated for the common person, and an appearance offering is stated for the Most High. Just as the festival offering stated for the common person is of what is fitting for him, so the appearance offering stated for the Most High is of what is fitting for Him; and so it is fitting that your table not be full while your Master's table is empty. "And they shall not appear before Me empty": with animal sacrifices. Or perhaps only with libations? You may reason thus: rejoicing is stated regarding a person, and rejoicing is stated regarding peace offerings; just as there it is with animal sacrifices, so here it is with animal sacrifices.
The Festival Offering Must Be Animal Sacrifices Not Birds or Meal
Yalkut Shimoni on Torah 356:2
וְלֹא יֵרָאוּ פָנַי, בִּזְבָחִים, אוֹ אֵינוֹ אֶלָּא בְּעוֹפוֹת וּבִמְנָחוֹת, וְדִין הוּא, נֶאֱמַר חֲגִיגָה לָהֶדְיוֹט, וְנֶאֱמַר רְאִיָּה לַגָּבוֹהַּ, מַה חֲגִיגָה הָאֲמוּרָה לָהֶדְיוֹט זְבָחִים, אַף רְאִיָּה הָאֲמוּרָה לַגָּבוֹהַּ זְבָחִים. וּמַה זְבָחִים, עוֹלוֹת. אוֹ אֵינוֹ אֶלָּא שְׁלָמִים. וְדִין הוּא, נֶאֱמַר חֲגִיגָה לָהֶדְיוֹט וְנֶאֱמַר רְאִיָּה לַגָּבוֹהַּ, מַה חֲגִיגָה הָאֲמוּרָה לָהֶדְיוֹט בְּרָאוּי לוֹ, אַף רְאִיָּה הָאֲמוּרָה לַגָּבוֹהַּ בְּרָאוּי לוֹ, וְכֵן בְּדִין, שֶׁלֹּא יְהֵא שֻׁלְחָנְךָ מָלֵא וְשֻׁלְחַן רַבְּךָ רֵיקָם. וְלֹא יֵרָאוּ פָנַי, בִּזְבָחִים, אוֹ אֵינוֹ אֶלָּא בִּנְסָכִים, הֲרֵי אַתָּה דָן, נֶאֱמַר שִׂמְחָה בְּאָדָם, וְנֶאֱמַר שִׂמְחָה בִּשְׁלָמִים, מַה לְּהַלַּן בִּזְבָחִים, אַף כָּאן בִּזְבָחִים.