הלכה על כתובות 94:13

Not to reduce her flesh, covering and time period: That anyone who acquires a Hebrew bondwoman and designates her may not reduce her flesh, her covering and her time period. And the explanation (Ketuvot 47b) of "flesh" is food, of "covering" is like its simple understanding and of "time period" is the way of the world (conjugal rights). And included in this negative commandment are all daughters of Israel (as well), not to reduce from them any thing from these [categories]. [This inclusion] is a fortiori (kal ve'chomer): If he does not reduce for [bondwomen], all the more so for free [women]. And [about] that which it is written (Exodus 21:9), "like the statute of the daughters he shall do for her" - they said in the Mekhilta d'Rabbi Yishmael 21:9:2 that it came to learn [from the others], but it ends up to teach, as the [law of the other] daughters are learned form her.