Why should one have marital relations as if forced by a demon?

Question

The gemarah (nedarim 20b) mentions that one of the reasons for having beautiful children is due to having relations "as if forced by a demon". Rashi there explains the term as either indicating that the act is performed forcefully or in a completely covered way as if hiding from a demon. This is codified in the halacha (shulchan aruch, orach chaim 240:9) where it is explained differently as either performing the act in fear or under duress.

I would like to understand this concept

1. How did this go from being a 'segulah' (charm) for having beautiful children to a compulsory halacha?
2. What is this business with demons? If the intent is to perform the act in any of the ways described above, why not just say so? What relevance do demons have over here?
3. Why does the Shulchan Aruch explain the implications of 'being forced by a demon' differently than Rashi? Where does he get this explanation from?
4. Why, in fact, must one perform this mitzvah in a way that would seem like it is against his will? Usually, we are encouraged to be happy in our performance of mitzvot. Why not here?
5. What is the woman's role here? Should she also feel compelled by a demon?
6. This does not seem to conform with the behavior of Rav when he slept with his wife (brachos 62a).

Answer 1

1. It is not a compulsory halacha but rather a recommended practice for someone who is concerned with his soul, as stated at the end of the Sif - וצריך בעל נפש ליזהר בהם.
2. There is a perspective (like it or not) that part of the sexual act involves accessing urges that are less than holy. Yes marital union is holy etc, but it borders very closely with some of our basest urges, which the torah proscribes indulging in. This dual nature is rare, seemingly only found with the sexual drive and the drive that underpinned prophecy/idol worship (cf. Yoma 69a). If one was not aware of the 'demonic' pitfalls then performing the act in accordance with halacha may miss the greater point; which is that you need to be careful, you're playing with fire here.
3. My guess would be that he is offering his own advice on how to deal with your yetzer in this situation. It is in the same spirit as that of Rashi, meaning that it acknowledges the danger inherent in the act and prescribes practical steps to avoid improper behavior.
4. No one is saying you can't perform the mitzvah out of joy, but there are many mitzvot that we are cautioned to take very seriously (davening for example).
5. Simply put the woman does not have the same restrictions because her yetzer hara is not the same as a man's. That's not to say that a woman does not have restrictions imposed on her to prevent her from indulging in base sexual desires, this just isn't one of them
6. My guess would be that this falls in line with the gemarah (Kesubos 17a) about amoraim who would dance while touching a kallah because they felt no inappropriate sexual desire toward her. Rav may have conquered his baser sexual instincts and was able to relate to his wife in a purely holy way during the act of sleeping with her.

Answer 2

The Ba'al HaTanya writes in Torah Or about this Halacha:

אך דהנה ידוע שהדבר שברצון נק' פנים ומה שהוא נגד רצונו נק' אחור ובשעת מ"ת היה כל רצון ישראל אליו ית' וכל עניני הגוף היה בבחי' אחור. כמארז"ל על כל דבור פרחה נשמתם ובאמת היה להם גופים. אך לפי שכל עניני הגוף היה בבחי' אחור ונמצא כמו שאין להם גופים וממילא היו בבחי' פנים כמים הפנים וגו' וכמ"ש ועל דמות הכסא דמות כמראה אדם ואיך שייך אצלו ית' כמראה אדם. אך הנה למשל כשאדם אוהב את חבירו חקוקה צורתו בלבו כאלו צורתו עליו. ועכשיו ג"כ צ"ל כל דבר גופני בבחי' אחור כמארז"ל גבי זיווג כאלו כפאו שד. וק"ו אצל שארי דברים ולא כמו שמדמין העולם שזהו דבר מאוס מפני שצריך טבילה אח"ז לא כן כי הוא דבר גדול וגם למעלה הוא דבר גדול וק"ו אצל אכילה וש"ד שצ"ל כאלו כפאו שד ולא לומר שזה אינו יכול לאכול כו'. וממילא יהי' פב"פ

It is known that something desired is called the face and what is not desired is called back [he then goes on to describe the idea of being face-to-face with G-d at the giving of the Torah]. And now [i.e. not just at the giving of the Torah, but today as well] every material matter has to be in the manner of "back", like the sages say regarding marital relations "as if a demon is forcing him". And all the more so other matter. Not like the world things that this [i.e. marital relations] is a disgusting thing because it requires immersion in the mikva afterwards - this is not so - rather it is a great/important thing and also above it is a great/important thing so how much more so concerning eating and other things that it has to be as if a demon is forcing him but he should not say that "he is not able to eat etc.". And then [his relationship with G-d] will be face to face.

Answer 3

Sefer Kaf Hachaim seems to maintain that the primary interpretation is like the first opinion recorded in the Shulchan Aruch: ודומה כמי שכפאו שד פי' באימה וביראה - in awe and fear [of Heaven]. And it's also quite clear that he's discouraging the practice of any of the other interpretations. This would seem to properly address your questions 4, 5, and 6 above:

4. Yes, you can enjoy the act while maintaining an awareness of God
5. No, the wife doesn't (and in my opinion, for the sake of having a healthy marriage in contemporary Western civilization, she probably shouldn't) even need to know about it
6. And, it conforms well with the behavior of Rav as his wife didn't need to be aware of his thoughts during the act

• As for your first question, user not-allowed to change my name's answer addressing this question applies to this answer here as well.

• I wouldn't know how to answer your second question without saying drush.

• And this answer here wouldn't help you with your third question either.

---

Incidentally, for the sake of staying sane in contemporary Western civilization, the husband might want to limit this specific practice to those times that his wife can actually conceive. But that's just my own thought.

Answer 4

I can see that your point 4 hasn't been answered with the most basic answer - the gemara's answer:

ואמרתי לו: מה טעם? ואמר לי: כדי שלא אתן את עיני באשה אחרת, ונמצאו בניו באין לידי ממזרות.

And I said to my husband: What is the reason for this behavior? And he said to me: It is so that I will not set my eyes on another woman, i.e., think about another woman; if a man thinks about another woman during sexual intercourse with his wife, his children consequently come close to receiving a mamzer status, i.e., the nature of their souls is tantamount to that of a mamzer. Therefore I engage in sexual intercourse with you at an hour when there are no people in the street, and in this manner. [Steinsaltz translation in bold, Steinsaltz commentary in non-bold]

He was very strict to not think about another woman, for the sake of his children. The manner was therefore a technique to keep bad thoughts out of his heart, and ensure his kavana was correct.