(Beraisa - R. Shimon ben Gamliel): Just like Terumah makes a Chazakah for Kehunah, so Ma'aser Rishon is a Chazakah for Leviyah. (The Yerushalmi does not hold that Ezra fined the Leviyim - SHA'AREI TORAS ERETZ YISRAEL);

One who receives a share [of Terumah from an inheritance] according to Beis Din, it is not a Chazakah for Kehunah. I can say that it came to him through his mother's father, who was a Kohen.

R. Yishmael bei Rebbi Yosi said, I never testified. Once I testified, and I [almost] established a slave for Kehunah!

R. Yitzchak ben Chakulah and R. Shimon b'Ribi - one of them established a brother through [testimony of] his brother, and one of them established a son through his father. One was for Kehunah, and one was for Leviyah.

A man came in front of Rebbi, and said 'this is my son. He is a Kohen.'

Rebbi: He is [established to be] your son. He is not [established to be] a Kohen.

Question (R. Chiyah Rubah): If you believe him that he is his son, believe him that he is a Kohen. If you do not believe him that he is a Kohen, do not believe him that he is his son!

Answer (Rebbi): [I believe him that] he is his son, but I say that [perhaps] he is the son of a divorcee or Chalutzah (a Chalal, who lacks Kedushas Kehunah).

Note: Perhaps R. Chiyah thought that this is unreasonable, for we are not concerned lest the father transgress(ed) both Arayos and lying.

(R. Avin): So [R. Chiyah Rubah] said to [Rebbi. Indeed, perhaps the Torah believed a father to identify his children for Mamon (inheritance), but not for Isur. Even so,] if you believe him that he is his son, [automatically you] believe him that he is a Kohen. If you do not believe him that he is his son, believe him that he is a Kohen, and this is like distanced testimony (of a stranger, not of a relative), and he is believed about him (one witness establishes Kehunah)!

Rebbi told R. Chiyah, [I believe him that] he is his son, but I say that [perhaps] he is the son of a divorcee or Chalutzah.

Assumption: Did not R. Yitzchak ben Chakulah and R. Shimon b'Ribi, one of them established a brother through his brother, and one of them established a son through his father? Let us say that since R. Shimon b'Ribi established a brother through his brother (presumably, he holds like his father, who does not establish a son through his father, R. Yitzchak ben Chakulah established a son through his father)!

Rebuttal: You can even say that [R. Shimon b'Ribi established] a son through his father, for Leviyah. (There is no concern for a Chalal.)