Reference for Meilah 3:3
רַבִּי יִשְׁמָעֵאל אוֹמֵר, הַדָּם, קַל בִּתְחִלָּתוֹ וְחָמוּר בְּסוֹפוֹ, וְהַנְּסָכִים, חֹמֶר בִּתְחִלָּתָן וְקַל בְּסוֹפָן. הַדָּם, בַּתְּחִלָּה אֵין מוֹעֲלִים בּוֹ. יָצָא לְנַחַל קִדְרוֹן, מוֹעֲלִים בּוֹ. הַנְּסָכִים, בַּתְּחִלָּה מוֹעֲלִים בָּהֶן. יָצְאוּ לַשִּׁיתִין, אֵין מוֹעֲלִים בָּהֶם:
Rabbi Yishmael says, blood [of sacrifices] is lenient at the beginning and stringent at the end, but libations are stringent at the beginning but lenient at the end. Blood, at the beginning is not subject to <i>meilah</i>, but once it goes out [of the Temple] to the Kidron valley it does become subject to <i>meilah</i>. Libations, at the beginning are subject to <i>meilah</i> but once they have run off into the pits [located beneath the altar] they are no longer subject to <i>meilah</i>.