Kesuvos4: 8
לֹא כָתַב לָהּ: ,,אִם תִּשְׁתְּבַאי, אֶפְרְקִינָךְ וְאוֹתְבִינָךְ לִי לְאִנְתּוּ”, וּבְכֹהֶנֶת, ,,אַהְדְּרִינָךְ לִמְדִינְתִָךְ” — חַיָּב, שֶׁהוּא תְנַאי בֵּית דִּין.
[If] he did not write for her: “If you are captured, I will ransom you and keep you for me as a wife,” or —- in the case of a Kohen’s wife —- “I will bring you back to your city,” he is [nevertheless] liable, since it is a condition established by the court.