Positive commandment · Mitzvat Aseh #180 of 613
To do to the collusive witness like he colluded
לעשות לעדים זוממין כמו שזממו לעשות
The verse · Devarim 19:19
וַעֲשִׂיתֶם לוֹ כַּאֲשֶׁר זָמַם לַעֲשׂוֹת לְאָחִיו וּבִעַרְתָּ הָרָע מִקִּרְבֶּךָ
“then shall you do to him, as he had thought to have done to his brother: so shalt thou put the evil away from among you.”
The Rambam’s words
To [punish] false witnesses [by] giving them the same penalty that they wish to have imposed [on the defendant], as [Deuteronomy 19:19] states: "And you shall do to him what he plotted to do to his brother."
לעשות לעדים זוממין כמו שזממו לעשות, שנאמר: "ועשיתם לו, כאשר זמם" (דברים יט,יט).
Why · Sefer HaChinuch #524
To do to the collusive witness like he colluded
“It is from the roots of the commandment [that it is] to punish any man whose heart became full to testify about a matter that he does not know truthfully and clearly — in that the matter is something that everything that belongs to the creatures, whether monetary or physical, depends upon.”
Who & when
“And this commandment is practiced in the Land of Israel at the time that we have an ordained court, since the payments of collusive witnesses are a penalty — and it is well-known that we only judge cases of penalties with an ordained court.”
Where in the Mishneh Torah
Hilchot Testimony הלכות עדות