Sanhedrin 25B

קים לי בנפשאי דידענא טפי. אבל תולה בדעת יונו ⁠– אימא לא.

I am certain of myself that I know better than my competitor how to win. But with regard to one who makes it dependent on the decision of his pigeon, say that he is not disqualified from bearing witness, as he is aware that he cannot guarantee the results and therefore resolves to transfer the money if he loses.

ואי תנא תולה בדעת יונו, דאמר: בנקשא תליא מילתא, ואנא ידענא לנקושי טפי. אבל תולה בדעת עצמו ⁠– אימא לא. צריכא.

And conversely, had the Mishnah taught this halakha only with regard to one who makes it dependent on the decision of his pigeon, one might assume that only this type of gambler is disqualified, as he presumably says: The matter, i.e., the race, is determined by knocking on trees and other objects to speed up the pigeons, and I know how to knock better than my opponent. Therefore, he does not resolve to transfer the money if he loses. But with regard to one who makes it dependent on his own decision, say that he is not disqualified from bearing witness, as the roll of the dice is pure chance. Therefore, it is necessary for the Mishnah to teach both cases.

מיתיבי: המשחק בקוביא ⁠– אלו הן המשחקים בפסיפסים. ולא בפסיפסים בלבד אמרו, אלא אפילו קליפי אגוזים וקליפי רימונים.

The Talmud raises an objection to the opinion that the expression: Those who fly pigeons, refers to an ara, from a baraita: With regard to the expression one who plays with dice, these are ones who play with pispasim, which are dice of marble or other types of stone. But the rabbis did not mean to say that only one who plays with pispasim is disqualified from bearing witness, but rather even one who plays with nutshells or pomegranate shells is disqualified.