משנה אויף דברים 19:19

How do witnesses become liable [to punishment] as perjurers?[If they say:] “We testify that so and so [a priest] is a son of a woman who had [formerly] been divorced or a haluzah,” it is not said that each witness should himself be as if he was born of a divorcee or a haluzah; rather he receives forty [lashes]. [If they say]: “We testify that so and so is guilty of [a crime entailing] exile”, it is not said that each witness should himself be exiled; rather he receives forty [lashes]. [If they say:] “We testify that so and so divorced his wife and has not paid her kethubah” seeing that either today or tomorrow he [the husband] will pay her kethubah, the assessment should be made how much a man will be willing to pay [now] for the ownership of her kethubah, on the condition that if she should be widowed or divorced [he will take it over] but if she should die, her husband will inherit her [estate including the kethubah]. [If they say]: “We testify that so and so owes his friend one thousand zuz on the condition that he will pay him within thirty days”, while the debtor says “ten years”, the assessment should be made how much a man is willing to pay for the use of a thousand zuz, whether he pays them in thirty days or ten years.

[If they say:] “We testify that so and so is liable to a flogging of forty lashes, and they are found to be perjurers, they receive eighty lashes, because of, “You shall not bear false witness against your neighbor” (Exodus 20:13) and “You shall do to him as he schemed to do to his fellow” (Deuternomy 19:19), these are the words of Rabbi Meir. But the sages say, “They receive only forty lashes.” Monetary impositions are shared among the offenders, but the lashes are not shared among the offenders. How so? If they testified that he owed his friend two hundred zuz, and they were found to be perjurers, they divide the corresponding damages proportionately between them. But if they testified that he was liable to a flogging of forty lashes and were found to be perjurers, each one receives forty lashes.

Perjuring witnesses are not to be put to death until [after] the end of the trial. Because the Sadducees say: “[Perjurers were put to death] only after the accused had [actually] been executed, as it says, “ A life for a life” (Deuteronomy 19:21). The [Pharisaic] Sages said to them: “But has not it already been said “You shall do to him as he schemed to do to his fellow” (Deuteronomy 19:19) which implies when his brother is still alive? If so, why does it say “A life for life”? For it might have been that perjurers are liable to be put to death from the moment their testimony had been taken, therefore the Torah states “A life for a life” that is to say that they are not executed until [after] the termination of the trial.