Before us is Mishnah 3 in the third chapter of Maseches Shevuos. This mishnah is similar in structure to the previous one, which dealt with a person who swore not to eat eight different items, except that here the mishnah deals with someone who swore not to drink and then drank various kinds of beverages - and here a certain distinction emerges between two forms of oath.
"Shevuah shelo eshteh" - "An oath that I will not drink," and afterward he drank many different beverages: he is liable for only one, since he took a general oath not to drink, and even though he drank different things, there is only one transgression of one oath here.
"Shevuah shelo eshteh yayin velo shemen velo devash" - "An oath that I will not drink wine, nor oil, nor honey," and he drank all three of them: he is liable for each and every one separately.
The question that needs clarification:
On the face of it, one could have explained that the person taking the oath does not list the beverages because he wants to make each of them a separate oath, but on the contrary - in order to exclude every other beverage: it is specifically these three that he swore about, but he sees no obstacle to drinking a different beverage, beer for example, which was not counted among them. In the previous mishnah it was required that he say "this loaf and this loaf," and by that very wording he reveals that they are separate from one another; whereas here his wording contains no such separation.
From where, then, do we know that his words are to be understood as separate oaths?
The Gemara's explanation - which case are we dealing with:
The Gemara explains that the mishnah is dealing only with a very particular case: his friend pressed him to come and drink with him, and specified in his urging: "Come and drink wine with me, come and drink oil with me, come and drink honey with me" (and it may be that honey water is meant), "and I want you to drink all three of these beverages with me." In response to this, the man swore that he would not drink these things.
Now, the one taking the oath did not need to list each and every beverage separately. Since his friend had already identified and specified the three beverages, it would have been enough for him to say "I am not drinking at your place," or "I am not drinking anything you mentioned." From the fact that he took the trouble to specify each of the beverages on its own, even though he could have exempted himself with an all-inclusive expression, it is proven that his intent was for a separate oath to take effect on each and every one, and therefore he is liable for each and every one.
In summary: only in this specific case, where his friend's detailed urging came first, is his statement understood as separate oaths and he is liable for each and every one. But in an ordinary case, where he said on his own initiative "An oath that I will not drink wine and oil and honey," there is only a single oath here, and he is liable for only one.