Before us is Mishnah 8 in chapter 1 of Maseches Rosh Hashanah, which lists those who are disqualified from serving as witnesses for testimony about the new moon. Most of those listed here are not disqualified by Torah law, but only rabbinically. The Mishnah opens and says: "Eilu hein hapesulin" - these are the ones who are disqualified, and it proceeds to list them one by one.
"Hameshacheik b'kubya" - one who plays with dice:
Kubya is an ancient form of dice throwing, a game whose entire purpose is gambling, and one who gambles at it is rabbinically disqualified from testimony. Two approaches are offered for the reason of this disqualification:
The Gemara in Maseches Sanhedrin establishes that this refers to someone for whom this is his primary livelihood, and he has no other source of income or occupation. Such a person is defined as one who "eino osek b'yishuvo shel olam" - he does not take part in the settlement of the world; he is not a partner in building up the world and its economy, and since he contributes nothing of his own, he does not necessarily have any understanding of, or concern for, the difficulties people face in earning their livelihood. For that reason he is not a person who can be fully relied upon.
One who gambles and profits from his gambling is a robber by rabbinic law, since his gain is not a genuine gain, but money he took from his fellow on the strength of an 'asmachta'. An asmachta is a situation in which a person commits himself to pay money while relying on the assumption that he is going to win, and he has no intention whatsoever of paying if he loses. A commitment that is not wholehearted in his mind - taking money on its strength is considered robbery by rabbinic law.
"U'malveh b'ribis" - and one who lends with interest:
Lending with interest is forbidden by Torah law, but our Mishnah comes to include even one who transgresses a form of interest whose prohibition is only rabbinic. The Gemara in Maseches Bava Metzia discusses this: which interest this is, and which collection of interest is forbidden rabbinically.
"Mafrichei yonim" - those who race pigeons:
Two explanations are offered in defining this disqualification:
This refers to one who races pigeons in a competition, and the point of it is gambling. This disqualification falls into the same category as "hameshacheik b'kubya" - an idler who does not take part in the settlement of the world.
It does not refer to racing pigeons in a competition, but to one who keeps pigeons that have been trained to lure other pigeons away from their owners. This robbery is only rabbinic, because by Torah law a person is not considered a full owner of the pigeons in his dovecote; they merely make their home with him and are not truly his property, and therefore taking them is robbery by rabbinic law.
"V'sochrei sheviis" - and those who trade in produce of the seventh year:
Seemingly this prohibition is from the Torah, as it says: "And the Sabbath produce of the land shall be yours for eating" - for eating and not for commerce. However, our Mishnah can be understood in several ways in which the disqualification is only rabbinic:
Regarding the seventh year nowadays, whose obligation is not from the Torah but only rabbinic.
Regarding people who do not know at all that the matter is forbidden by Torah law.
Regarding people about whom it is not known with certainty that they traded in seventh year produce, but there is only a suspicion about them.
"Nashim va'avadim" - women and slaves:
The slave mentioned here is an eved kena'ani, a non-Jewish slave, who is obligated in mitzvos to the same degree that a woman is obligated in them and is exempt from time-bound positive mitzvos. However, the disqualification of women and slaves from testimony is not rabbinic like the other disqualifications listed here, but a Torah law - they are disqualified by the Torah itself.
The principle at the conclusion of the Mishnah:
The Mishnah concludes: "Zeh haklal: kol eidus she'ein ha'ishah kesheirah lah, af hein einan kesheirin lah" - this is the rule: any testimony for which a woman is not fit, they too are not fit for it. All those disqualified individuals listed in our Mishnah are unfit for those testimonies for which a woman is unfit. But testimony for which a woman is fit - such as a woman who testifies about another woman that her husband has died, so that she may remarry - for that they too are believed, and one may rely upon them in these types of testimony.
In summary: In this Mishnah we listed those disqualified from testimony about the new moon: one who plays with dice, one who lends with interest, those who race pigeons and those who trade in seventh year produce - whose disqualification is rabbinic, either because they do not take part in the settlement of the world or on account of rabbinic robbery; and women and slaves - whose disqualification is from the Torah. And the Mishnah gave us a rule: any testimony for which a woman is not fit, they too are not fit for it, and for testimony for which a woman is fit - they too are fit and believed.