Reference for Zevachim 8:7

נִתְעָרֵב בְּדַם פְּסוּלִין, יִשָּׁפֵךְ לָאַמָּה. בְּדַם תַּמְצִית, יִשָּׁפֵךְ לָאַמָּה. רַבִּי אֱלִיעֶזֶר מַכְשִׁיר. אִם לֹא נִמְלַךְ וְנָתַן, כָּשֵׁר:

[If blood] was mixed with blood of invalid sacrifices, it is poured out in the drain. [If it was mixed] with the animal's final blood [that emerges following its slaughter], it is poured out in the drain. Rabbi Eliezer deems it valid. If [the priest] did not consult and applied the blood [mixture] it is valid.

Jastrow