I recently took a survey of many young couples my age in an effort to determine what exactly we had all been taught in our Chosson and Kallah classes. Were our lessons similar? Did they differ in any extreme way? I discovered something disturbing- namely, that nearly everyone was totally ignorant of two very important sources. To be completely blunt and very honest, I am going to discuss intimacy and sexuality here. If this troubles you, please don't read further.
The first source that people had not been taught is the Ri to Yevamos 34b.
The gemara is discussing various sexual practices and focuses specifically on Er and Onan and the fact that apparently they engaged in unnatural intercourse (shelo k'darkah). A question is raised by Tosfos: What of the gemara in Nedarim 20b? There it says:
R. Johanan said: The above is the view of R. Johanan b. Dahabai; but our Sages said: The halachah is not as R. Johanan b. Dahabai, but a man may do whatever he pleases with his wife [at intercourse]: A parable; Meat which comes from the abattoir, may be eaten salted, roasted, cooked or seethed; so with fish from the fishmonger.4 Amemar said: Who are the 'Ministering Angels'? The Rabbis. For should you maintain it literally, why did R. Johanan say that the halachah is not as R. Johanan b. Dahabai, seeing that the angels know more about the formation of the fetus than we? And why are they designated 'Ministering Angels'? — Because they are as distinguished as they.5The same way that a man may eat meat in whichever manner he pleases- whether it be salted, roasted, cooked or seered- so too may a man do with his wife whatever he pleases (as long as it is mutual and consensual). The question Tosfos raises is that there seems to be a contradiction- in Nedarim we say that a man can do whatever he wishes, yet here in Yevamos we are taking issue with Er and Onan and the fact that they engaged in "unnatural intercourse."
A woman once came before Rabbi and said, 'Rabbi! I set a table before my husband, but he overturned it.' Rabbi replied: 'My daughter! the Torah hath permitted thee to him — what then can I do for thee?'
The answer is that in fact we are not taking issue with the fact that Er and Onan engaged in unnatural intercourse. Wherefore were these two brothers punished? The explanation we can offer is because A) one brother practiced this spilling of seed as coitus interruptus in order to ensure that his wife would never become pregnant, and this form of birth control is forbidden B) the wife of one's brother is generally forbidden to a man and the only case in which he may take her is if he plans to build up his brother's family through her= Yibum; the fact that this brother was spilling his seed showed he had no interest in actually fulfilling the mitzvah of Yibum and thus was guilty of one of the forbidden relations.
This means that shelo k'darkah (insofar as it may mean coitus interruptus) is forbidden when it is used as a method of birth control. However, as the Ri explicitly states, "if a man's desire is for his wife in this particular way (shelo k'darkah inasmuch as it means spilling seed) and he only does this sometimes, but not every time (i.e. not as a method of birth control, for instance) then it is permitted."
But what's more, this issue is raised by none other than the great Gadol R' Moshe Feinstein himself.
This appears in Even Ha'Ezer Samach-Gimmel.
R' Moshe explains that when it speaks of "motzi zera l'vatalah" - wasting seed, this is referring to a true waste of seed where there is absolutely no need for that seed to have been spilled. However, it is permitted to spill seed outside of the woman for the fulfillment of the mitzvah of Onah and in order to cause his wife to be joyous/ fulfilled (because then it's not l'vatalah, but rather for a purpose)! Because when it comes to the matter of relations between a man and his wife, the Torah permitted a man to do that which his heart desires which is shelo k'darkah because he considers it his need and it is not considered l'vatalah and in fact it is completely permitted. The reason it is only permitted sometimes (and not always), is because it will not always be a need or desire as oftentimes he will be satisfied from the k'darkah intimacy.
R' Feinstein goes on to quote the Ri and cites both of his provisions. The Ri offers two different opinions, one more stringent and one less so. 1) That he who deliberately intends to spill seed - it is assur (but if he comes to spill seed and had not intended it, that is fine) 2) If he commonly spills seed outside of the woman/ this is a regular thing for him to do, it is also assur because one does not crave this regularly. R' Feinstein follows the second approach of the Ri and explains that if someone sometimes desires to do this, it is muttar even if he does not have in mind that it should be for the sake of the mitzvah but rather only because it is a need between himself and his wife. That's pretty radical!
Now, why am I telling you this? Because Heshy's chosson teacher (if you want to learn with our teachers/ get their info, email me), who showed him these sources, explained that there are many couples who harbor desires to act with one another in a loving way that might also arouse the man to a point where he does not spill seed within the woman, but rather outside of her, and they believe they are bad people because of this. Alternatively, there are those who simply do as they wish and believe that they are breaking Torah law and halakha and thus struggle with a lot of guilt because they were never taught accurately.
What it comes down to is: Be intimate with your wife and make her happy and glad, and should you wish to sometimes (derech akrai) engage in behavior that is shelo k'darkah and which includes spilling seed outside of her rather than within her, that is perfectly muttar and fine. Just beware because if you do this every time or regularly it becomes a problem.
ADDENDUM: I thought this was obvious, but in case it wasn't: what I am presenting here are merely sources. Obviously you should ask your own rabbi, posek or halakhic decisor before following them, which is true of all my posts. Rock on.