Reference for Bekhorot 69:64
רועי ישראל והן כהנים נאמנין
WHEREAS PRIESTS SHEPHERDS ARE NOT TRUSTWORTHY.<span class="x" onmousemove="('comment',' For they are suspected of deliberately bringing about a blemish. tndk');"><sup>34</sup></span> R'SIMEON B. GAMALIEL SAYS: HE IS TRUSTWORTHY AS REGARDS SOMEBODY ELSE'S FIRSTLING, BUT HE IS NOT TRUSTWORTHY AS REGARDS HIS OWN. R'MEIR SAYS: ONE WHO IS SUSPECTED OF NEGLECTING ANY RELIGIOUS MATTER MUST NOT PRONOUNCE JUDGMENT ON IT NOR GIVE EVIDENCE CONCERNING IT. <big><b>GEMARA: </b></big>R'Johanan and R'Eleazar [differ as to the interpretation of the Mishnah]. One explains it [as follows]: The expression 'LAY ISRAELITE SHEPHERDS' means [lay Israelites] in the employ of priests are trustworthy, for we do not apprehend that their testimony may be influenced by their bread and butter.<span class="x" onmousemove="('comment',' I.e., by their dependence on their employers. ; means lit., 'quaffing', and in general eating and drinking. Aliter: by the share they would have in the firstling when slaughtered.');"><sup>35</sup></span> The expression 'PRIESTS' SHEPHERDS means: [shepherds who are priests] in the employ of Israelites are not trustworthy, since the shepherd might Say.' Since I work for him, he will not pass over me and give it to another'.<span class="x" onmousemove="('comment',' And therefore we suspect them like the priest owners of causing a blemish.');"><sup>36</sup></span> And the same ruling [of the testimony being untrustworthy] applies to [a shepherd who was] a priest with reference to [the firstling of] another priest 'for we suspect them of favouring each other.<span class="x" onmousemove="('comment',' Thinking that by giving favourable evidence for his firstling now, he will on some future occasion be repaid when having obtained an unblemished firstling from an Israelite, he will make it blemished and this priest will testify that the blemish appeared of itself on the animal.');"><sup>37</sup></span> And thereupon R'Simeon comes and says: HE IS TRUSTWORTHY AS REGARDS SOMEBODY ELSE'S FIRSTLING,<span class="x" onmousemove="('comment',' Whether his master's or belonging to another.');"><sup>38</sup></span> BUT HE IS NOT TRUSTWORTHY AS REGARDS HIS OWN.<span class="x" onmousemove="('comment',' Where an Israelite had already given him a firstling.');"><sup>39</sup></span> And R'Meir then adds: HE WHO IS SUSPECTED OF DISREGARDING ANY RELIGIOUS MATTER MUST NOT PRONOUNCE JUDGMENT ON IT NOR GIVE EVIDENCE CONCERNING IT. But the other [teacher] explains it [as follows]: The expression ISRAELITE SHEPHERDS means: [Shepherds of Israelite sheep] even if priests, are trustworthy.