Halakhah for Sanhedrin 170:5

It is also appropriate for us to attach this preface: And that is that anything for which one is liable a death penalty of the court or excision is perforce a negative commandment - except for the Passover (sacrifice) and circumcision. For they involve excision, even though they are positive commandments - as they said at the beginning of Tractate Keritot (Keritot 2a). But besides them, there are absolutely no positive commandments for which one who transgresses them would be liable for excision; all the more so a death penalty of the court. And anything about which it appears in the Torah, that if one does a certain action, he is to be killed or become liable for excision - it is certainly known that this act is prohibited and that it is a negative commandment. But behold sometimes Scripture explains the punishment alongside the prohibition, such that it explains the punishment and the prohibition. For example, the desecration of Shabbat and idolatry - about which it states, "you shall not do any work" (Exodus 20:10), and "you shall not worship them" (Exodus 20:5); and afterwards renders the one who does work [on Shabbat] or who worships idolatry liable for stoning. And sometimes the prohibition is not made clear as a definite negative commandment in Scripture; but He rather mentions the punishment and omits the prohibition. But the principle amongst us is that Scripture does not punish [for something] unless it prohibited [it], and that it is impossible not to have a prohibition for anyone who is liable a punishment. And hence, it is said in every place, "We have heard the punishment; from where [do we know] the prohibition? [Hence] we learn to say, such and such." And when the prohibition is not in Scripture, it is learned out by one of the Talmudic methods - like that which they mentioned about the prohibition of cursing one's father and mother and of striking one's father and mother, which is not explicit in Scripture at all. As it did not say, "You shall not strike your father." Yet it made one who strikes or curses liable for a death penalty. Hence we know that they are negative commandments; and we derived the prohibition for them - and those like them - from other places, by way of analogy. And this does not contradict their saying, "We do not derive a prohibition from an inference," nor their always saying, "And can we derive a prohibition from a derivation?" For we only say, "We do not derive a prohibition from an inference," regarding the derivation from an analogy of a prohibition that is not understood at all. However when we find the punishment for one who does this action explicit in the Torah, we perforce know that it is a forbidden action from which we are prohibited. Yet we regardless derive it from an analogy, so that the principle of their saying, "Scripture did not punish [for something] unless it prohibited [it]," be reinforced. But once the prohibition has come to us - not to do that thing - the one who transgressed and did [it] will become liable for excision or death. And know this principle and guard it together with the previous ones, to remember it in all that is coming up.

He prohibited us from exploiting a captive woman (yefat toar) after one has sexual intercourse with her. [This] means to say that he does not work her and leave her to be like one of the other maidservants that serve as slaves. And that is His saying, "you shall not exploit her, since you have afflicted her" (Deuteronomy 21:14). And the language of the Sifrei (Sifrei Devarim 214:5) is, "'You shall not exploit her' - you shall not use her." Behold it has been made clear to you that these two negative commandments are prohibiting two separate matters. And that is that He prohibits from selling her to someone besides him; and also from leaving her with him in the manner of slavery. Rather he should do, like that which He, may He be exalted, commanded - "you shalt let her go where she will." And so did they explain in Sanhedrin (Sanhedrin 85b) about one who kidnaps a soul, from His saying, "and he exploited him and sold him" (Deuteronomy 24:7). They said, "It is from when he brings him into his domain and uses him." And the laws of the captive woman have been explained in the first [chapter] of Kiddushin. (See Parashat Ki Tetzei; Mishneh Torah, Kings and Wars 8.)

Not to make her serve after he has intercourse with her: That we should not make a [captured] 'woman of beautiful form' serve, after intercourse with her. And about this it is stated (Deuteronomy 21:14), "you shall not abuse (titaamer) her, since you afflicted her." The explanation of "abuse" is that is an expression of service. And so did they say in Sifrei, "'You shall not abuse her' - you shall not take service from her." And the matter is that we should not set her up as a concubine or as maid-servant in bondage. And the matter of the verse is not that we should not have her serve any service that women do for their husbands. [Rather] Scripture prohibits making her into a maid-servant, [just] like it is also forbidden to sell her as a maid-servant, and the intention is one. And so too with the stealing of a soul from his brothers (kidnapping), about which it is written (Deuteronomy 24:7), "and he abused (hitaamer) him" - they, may their memory be blessed, explained (Sanhedrin 85b), that [it means that] he brought him into his domain and made him serve.