Reference for Menachot 109:9

אמר רב פפא שמע מינה דחקינן ומוקמינן מתניתין בתרי טעמי ולא מוקמינן בתרי תנאי

Must we then say that in the case of the first clause there is no priest present whilst in case of the second clause there is a priest present? - Yes. In the case of the first clause there is no priest present but in the case of the second clause there is a priest present.

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