Drinking Between Glasses of Wines at the Passover Seder

They mixed for the third cup and he recites the blessing over his food. The fourth [cup of wine], one completes hallel over it and recites the blessing of the song upon it. If one wants to drink between these cups, one may drink, but not between the third and fourth cups.

And, if one wants to drink - even many cups - he may do so. But, Rabbi Eliezer ben Yoel HaLevi of Bonn (1140–1225) wrote as long as one intends to not bless a second time, which would look as if one was adding to the cups.

After eating the afikoman, we mix the third cup and bless the Grace After Meals and Creator of the fruits of the vine upon it, then one drinks it while reclining. And one neither blesses a post-consumption blessing upon this third cup, nor should one drink wine between the third cup and the fourth cup.

RAMA: However, one is able to drink many times from the third cup and all of it is considered as one drinking, even though one interrupts between these drinkings. ...

RAMA: One should neither eat more than sufficiently nor drink more than appropriately, so that one should not eat the afikoman with coarse eating or even to get drunk and sleep immediately.

And if he wants to drink, he can drink even many, he has permission to do so, which derives from a mishnah that between these cups if one wants to drink, he can drink between the third and the fourth, he shall not drink, etc. And Rabbi Samuel ben Meir (1085-1158) wrote that "in the Yerushalmi..., but what one drinks prior to the meal does not intoxicate; therefore, even between the first two cups, one can drink." But what Rabbi Ya'akov ben Asher wrote [in the Tur] that one can drink, even many, since it will not intoxicate. And similarly has Rabbi Mordekhai ben Hillel HaKohen (1250–1298) written. And he wrote further that between the first and second cups, there is a mitzvah aspect to such drinking a lot, since it generates hunger and one may eat enjoyably eat matzah, which is not as is written in the Kol Bo​​​​​​​.

Lest he get drunk and sleep and not finish the Hallel. And some wrote the reason is because it seems to add to the glasses. And early modern period rabbinic authorities wrote that it does not mean specifically wine; this is the case for other intoxicating beverages. However, if it is not an intoxicating beverage, it is permissible, as long as it is not the wine of the land; that if it were the wine of the land, one should be stringent and concern for the second reason: that it appears as if one is adding to the [statutory four] glasses [of wine for the Seder].

Refer to the Mishnah Berurah what is written with regards to the wine of the land and know that the concluding language of the Mishnah and all rabbinic authorities that it is implied that one should not drink even a little bit. Indeed, all of this is according to the reasoning of the Talmud Yerushalmi, which is on account of drunkenness; for this, the sages did not permit even any drinking beyond the four cups. Indeed, on the other hand, for the other reason that it appears that one is adding to the cups; if so, it is possible that it is only referring to when one is drinking the minimum amount for a cup, which is not the case for Rabbi Moshe Isserles. And everything is considered as one drinking, which means to say even if there was still a quarter-log remaining [in one's cup]. But this requires further inquiry.

And all of this is between the cups, but if he poured the cup and began to expound upon the haggadah, one is not permitted to interrupt in the middle of it, which is what Rabbi Moses ben Naḥman (1194-1270) wrote; and similarly wrote Rabbi Nissim ben Reuven of Girona (1290-1376). And its further inferrable from his words that even if one had not yet begun the haggadah, just simply that they had poured the cup and prepared to say the haggadah, that would also be forbidden. But Rabbi Zeraḥiah ben Isaac ha-Levi Gerondi (1115-1186) permitted in all of these situations. And similarly have the Tosafists written that it is specifically with Hallel or the blessing of asher ga'alnu that it is prohibited (Pes. 103b). But Rabbi Karo categorically writes according to what Rabbi Moses ben Naḥman wrote, even for a mitzvah cup....

Such as he forgot and did not make Havdallah (for when the Seder occurs on a Saturday night) and did not remember until he drank the first cup [to do that], or such that his bowels are heavy on him, or that he wants to drink more in order to increase his appetite to eat matzah hungrily and similar such matters.