Positive commandment · Mitzvat Aseh #220 of 613
The commandment on the court to judge the case of a seducer
לדון במפתה בחמישים שקל עם שאר דינין
The verse · Shemot 22:15
וְכִי־יְפַתֶּה אִישׁ בְּתוּלָה אֲשֶׁר לֹא־אֹרָשָׂה וְשָׁכַב עִמָּהּ מָהֹר יִמְהָרֶנָּה לּוֹ לְאִשָּׁה
“And if a man seduce a virgin that is not betrothed, and lie with her, he shall pay the bride price for her to be his wife.”
The Rambam’s words
To carry out the judgment concerning a seducer, fining him fifty shekels and carrying out the other laws regarding this matter, as [Exodus 22:15] states: "If a person will seduce...."
לדון במפתה בחמישים שקל עם שאר דינין, שנאמר: "כי יפתה איש" (שמות כב,טו).
Why · Sefer HaChinuch #61
The commandment on the court to judge the case of a seducer
“The root of the commandment is well-known. And do not wonder here — since “all of the honor of the king’s daughter is inside” (Psalms 45:14), [how is it that] she is sold to the [seducer] for fifty silver pieces, whether she is wealthy or whether she is poor?”
Who & when
“And [it] is practiced in every place that there is a court of ordained judges, as we only judge cases of penalties with ordained judges.”
Where in the Mishneh Torah
Hilchot Virgin Maiden הלכות נערה בתולה