Ketubot 49B

דאפילו בתו, חובה הוא דליכא, הא מצוה איכא.

That even with regard to his daughter, there is no obligation to provide her sustenance, however, there is a mitzva to do so.

ואיבעית אימא רבי יהודה, והכי קאמר: האב אינו חייב במזונות בתו, וכל שכן לבנו. הא מצוה בבנו איכא, וקל וחומר לבנות. והא דקתני בתו ⁠— הא קא משמע לן דאפילו בתו חובה ליכא.

And if you wish, say that the Mishnah is in accordance with the opinion of R' Yehuda, and this what he said in the Mishnah: A father is not obligated to provide sustenance for his daughter, and all the more so he is not duty-bound to provide for his son. It may be inferred from here that there is at least a mitzva with regard to a son, and the same applies by a fortiori inference with regard to the daughters. And the reason that the Mishnah teaches the case of his daughter is because it teaches us this: That even with regard to his daughter there is no obligation, despite the mitzva to guard her from dishonor.

ואיבעית אימא רבי יוחנן בן ברוקא, והכי קאמר: אינו חייב במזונות בתו, והוא הדין לבנו. והוא הדין דאפילו מצוה נמי ליכא, ואיידי דבנות לאחר מיתת אביהן חובה, תנא נמי אינו חייב.

And if you wish, say that the Mishnah is in accordance with the opinion of R' Yoḥanan ben Beroka, and this is what he said in the Mishnah: A father is not obligated to provide sustenance for his daughter, and the same is true with regard to providing for his son. And the same is true with regard to a mitzva; there is not even a mitzva to feed either one’s sons or daughters, but since the tanna wanted to say with regard to daughters that after their father’s death there is an obligation to sustain them from his estate, he also taught in a parallel manner that the father is not obligated to provide sustenance for his daughters during his lifetime. Consequently, it is incorrect to infer from here that there is a mitzva to sustain them despite the lack of obligation; rather, the tanna means that there is no obligation and not even a mitzva to do so.