Ketubot, Chapter Two, Mishnah Seven
This mishnah illustrates the same principle employed in yesterdays mishnah, but uses the example of men who claim to be priests.
1) And likewise two men, [if] one says, I am a priest, and the other says, I am a priest, they are not believed.
2) But when they testify about one another, they are believed.
Section one: When each man claims to be a priest, neither is believed and neither will receive terumah. Just as in yesterdays mishnah, where a woman could not testify with regard to her own personal status, so too in todays mishnah a man cannot testify with regard to his own status.
Section two: However, if both men corroborate the others testimony they are believed.