Shevuot 32B

ומחלוקת בעדי סוטה ⁠– בעדי סתירה; מר סבר: דבר הגורם לממון כממון דמי ⁠– וחייב, ומר סבר: לאו כממון דמי ⁠– ופטור.

And there is a dispute with regard to witnesses in the case of a sota; this is referring to witnesses of seclusion who testify that the woman who was warned by her husband in fact entered into seclusion with the man in question. One Sage, R' Elazar, son of R' Shimon, holds that a matter that causes financial loss is considered to have monetary value, and each witness is liable for taking a false oath of testimony, as had they testified the woman would lose her marriage contract. And one Sage, the Rabbis, hold that a matter that causes financial loss is not considered to have monetary value, and he is exempt.

הכל מודים בשכנגדו חשוד על השבועה, הכל מודים בעד אחד דרבי אבא.

§ It is stated above further: All concede with regard to a witness testifying on behalf of the claimant when his counterpart is suspect about the oath. All concede in the case of one witness, as in the incident with R' Abba.

הכל מודים בשכנגדו חשוד על השבועה ⁠– דחשיד מאן? אילימא דחשיד לוה, דאמר ליה מלוה: אי אתית אסהדת לי, הוה משתבענא ושקילנא; ולימא ליה: מי יימר דמשתבעת?

The Talmud elaborates: All concede with regard to a witness testifying on behalf of the claimant when his counterpart is suspect about the oath. The testimony of one witness renders the borrower liable to take an oath that he does not owe money. The Talmud asks: In a case where who is suspect? If we say that the borrower who is denying the debt is suspect, and it is a case where the lender says to the witness: If you came and testified on my behalf I would have taken an oath and taken the sum owed me from the borrower, since he is suspect with regard to oaths, why would the witness be liable for taking a false oath of testimony? Let the witness say to the lender: Who could say that you would have taken an oath? Since there is no certainty that he would have taken the oath, the witness is merely the cause of a cause of financial loss.