Daf 66a

The gemara brings a dispute between R. Yoshiya and R. Yonasan concerning how we learn from the Torah that one is liable to the death penalty for cursing either one's father or one's mother.

It says in Vayikra (20,9) "A man who curses his father and his mother shall be put to death". R. Yoshiya says, I only know from this that he is liable if he curses both his father and his mother. From where do we know that if curses his father and not his mother, or his mother and not his father, that he is also liable? Says the Torah at the end of the posuk, "his father and his mother he has cursed, his blood is upon himself". His father he has cursed. His mother he has cursed. Rashi explains that he learns this from the fact that at the beginning of the posuk the Torah juxtaposed the word "curses" to "his father", and at the end of the posuk it juxtaposed "he has cursed" to "his mother".

But R. Yonasan disagrees and says that it implies both of them together, and it implies one by itself, unless the posuk specifies and writes the word "together". Note that his words are not specifically discussing this posuk - more about this later. Rashi explains that he learns everything from the beginning of the posuk, because even though the word "and" combines the word "his mother" to "his father", nevertheless, the posuk also implies each one individually, unless the posuk specifies and writes that they are "together". As it is written in Devarim (22) "You shall not plow with an ox and a donkey together" - specifying that it is only forbidden to plow with both of them together, so that you should not think that it means that it is forbidden to plow with either an ox or a donkey by themselves.

Tosafos is anazed at Rashi's explanation, because if so it is impossible to explain according to R. Yoshiya why the word "together" is written in the posuk in Devarim, since he would in any case learn that it is forbidden to plow only when both of them are together. Therefore, Tosafos explains that R. Yonasan does not learn the usage of the word "together" from a specific posuk, but rather he said this rule from his own logic.

Before I explain my understanding of this gemara, let me state two things which should be understood here. The first is that there is no dispute as to the halachah, since this is already known from the Oral Law, but rather the dispute is how we learn this from the written Torah. The second is that where there is some ambiguity in interpreting a posuk, we always have to interpret it stringently, unless there is an indication to learn otherwise. 

Now, the dispute between R. Yoshiya and R, Yonasan hinges around explaining why the Torah sometimes specifies the word "together", and sometimes not. It seems to me that R. Yonasan holds that the Torah writes the word "together" to indicate that the 'vav' is to be interpreted to mean 'and', and thus it follows that when this word is absent, the 'vav' means 'and/or'. Thus one is only forbidden to plow with an ox and a donkey together, but one is liable for cursing one's father and/or one's mother. This is a general rule of the Torah according to R. Yonasan, and this is why his words were not directed specifically at the posuk under discussion, as I pointed out earlier.

But R. Yoshiya disagrees, and holds that the 'vav' sometimes means 'and' and sometimes it means 'or', and there are no rules as to its interpretation, except the rule that I mentioned above, that we have be stringent in our interpretation. In the posuk which tells us that it is forbidden to plow with an ox and/or a donkey, if the Torah had not written the word 'together', we would have interpreted the 'vav' to mean 'or', in order to be stringent to forbid plowing with either an ox or a donkey, and since this is not the wish of the Torah, it wrote the word 'together'. But in our posuk concerning giving the death penalty, we would have interpreted the 'vav' to mean 'and', in order to be stringent and only put to death one who curses both his father and his mother, if not for the indication at the end of the posuk which teaches otherwise.

This explanation defends Rashi from the challenge of Tosafos.

I have one last comment on this gemara, and this concerns Rashi's explanation as to how R. Yoshiya learns from the end of the posuk that one is liable for cursing one's father or one's mother from the juxtaposition of the words. At this point in time I do not understand the logic of this explanation - how does the juxtaposition show this? Also, this explanation does not seem to fit with the words of the gemara, "his father he has cursed, his mother he has cursed". According to Rashi's explanation these words are completely superfluous.

I do not have an alternative explanation to offer, but I will present the observation that the gemara seems to be saying that since at the end of the posuk the verb of cursing comes after the subjects, as opposed to the beginning of the posuk where the verb precedes the subjects, the verb acts on each subject individually, and thus means "his father he has cursed, his mother he has cursed". However, knowing little about grammar, I do not know whether this observation is correct, so I offer it only as something to think about.