As we have learned, when someone claims that another person owes him money and the defendant denies that he owes all of the money, but admits that he owes part of it, then he is a modeh be-miktzat who must pay the amount that he admits to and then take an oath that he does not owe any more. The Gemara (daf 3a) brings the opinion of Rabbi Hiyya who rules that the same law would apply if the defendant denies owing any money but witnesses come and testify that he owes part of the money that is claimed. Here, too, according to Rabbi Hiyya, the defendant will have to swear that he does not owe the full amount, since the witnesses are no less believable than his own admission.
The Gemara on our daf tells of a shepherd who received animals to watch on a daily basis, and the individual who entrusted the animals to him always made sure that there were witnesses who saw him receive them. One day he gave the shepherd animals without witnesses, and when he came to take back his animals the shepherd denied having received them, but witnesses testify that he ate two of them. Rabbi Zeira argues that according to Rabbi Hiyya’s ruling the shepherd will have to pay for those animals and take an oath that he did not receive any others.
In response to Abaye’s objection that the shepherd cannot be allowed to take an oath, since he has already shown himself to be a thief, and thus untrustworthy, Rabbi Hiyya agrees that it is not the shepherd who will take an oath to deny the charges, rather the plaintiff will be permitted to swear that he gave him the animals and will be able to receive them based on that oath.
In Jewish law, oaths are not taken in court by witnesses, but by the defendant who, under certain circumstances, is obligated to either pay or satisfy the plaintiff by swearing that he does not owe money. The halakha is that if the defendant “owes” the plaintiff an oath, but he cannot take it for some reason (e.g. he is known to be untrustworthy), then the plaintiff would be permitted to swear that his claim is true, and the defendant will have to pay.