Ketubot, Chapter 4, Mishnah 11
Ketubot, Chapter Four, Mishnah Eleven
This mishnah discusses the clause in the ketubah which guarantees a wife that her daughters will be maintained from her husbands estate until they are married.
If he did not write for her, the female children that I will have from you will dwell in my house and be maintained out of my estate until they are taken in marriage, he is nevertheless liable, because [this clause] is a condition laid down by the court.
A husband is liable to support his wifes daughters until they are taken in marriage. As we learned above in mishnah six, this refers to after the husbands death. Even if he doesnt write such a clause in the ketubah, he is liable for it is a condition laid down by the court.