וַאֲנַ֗חְנוּ לֹ֥א נוּכַ֛ל לָתֵת־לָהֶ֥ם נָשִׁ֖ים מִבְּנוֹתֵ֑ינוּ כִּֽי־נִשְׁבְּע֤וּ בְנֵֽי־יִשְׂרָאֵל֙ לֵאמֹ֔ר אָר֕וּר נֹתֵ֥ן אִשָּׁ֖ה לְבִנְיָמִֽן׃ (ס)
Howbeit we may not give them wives of our daughters.’ For the children of Israel had sworn, saying: ‘Cursed be he that giveth a wife to Benjamin.’
Read halakhic rulings (Jewish law) on Judges 21:18: and classical halakhic sources.