The Sages stated (Pesaĥim 108b) that in order to fulfill the mitzva of the four cups properly, one must dilute the wine with water, because otherwise it will be too strong and cause intoxication. Though the alcohol in such wine gives one pleasure, the mitzva is to drink the wine in the manner of free people, that is, like wealthy people who have control of their own time and permit themselves to drink the best wine, making sure it is diluted properly so that one can enjoy it without getting drunk. Today’s wine is not as strong, and there is no need to dilute it. Even when it is necessary to dilute it, this is done at the winery. Therefore, there is no mitzva today to dilute the wine (MB 472:29).
Instead, nowadays we enhance the expression of our freedom by purchasing the finest wine that is strong enough to intoxicate, because such wine causes a sense of joy, liberation, and freedom. However, one must be careful not to use a wine so strong that it disrupts one’s ability to concentrate on the Hagada and to fulfill the mitzvot of the Seder night. One must therefore drink four cups of wine in a manner that brings joy and does not cause drowsiness or intoxication. If one fears that by drinking a full cup of regular wine he will be unable to concentrate properly while reading the Hagada, he should mix his wine with grape juice. This will allow him to drink wine that intoxicates, while properly fulfilling all the mitzvot of the Seder night. One who finds it difficult to drink wine that contains even just a small amount of alcohol may fulfill the mitzva by drinking grape juice (Mikra’ei Kodesh 2:35).
When the Sages instituted the four cups, they did not imagine that one would fulfill this mitzva with grape juice, as in their day there was no way to preserve the juice without it turning into vinegar. They wanted us to recite the Hagada and tell the Exodus story while drinking wine that enhances enjoyment. One who uses grape juice does not fulfill the mitzva in the way the Sages intended it. Even one who does not enjoy the taste of wine or who gets headaches from it must drink the four cups. In fact, the Gemara recounts that R. Yehuda b. Ilai had to wrap his head in a kerchief from Pesaĥ until Shavu’ot due to a headache caused by drinking four cups of wine (Nedarim 49b; SA 472:10; MB ad loc. 35). However, if wine will cause one to be ill and lie down he is exempt from this mitzva. Now that grape juice is available, even one who merely suffers from the effects of wine – for example, it gives him headaches – may discharge his obligation using grape juice.
Women are also commanded to drink four cups of wine, just as they are commanded to fulfill all of the mitzvot of the Seder night (SA 472:14). Le-khatĥila, they too should drink wine that maximizes enjoyment. However, if a woman fears becoming intoxicated, she may use grape juice to dilute or even completely replace the wine if she prefers.
The Sages also stated that there is a mitzva to seek out fine red wine (y. Pesaĥim 10:1). However, be-di’avad, any wine is adequate, even cheap white wine (SA 472:11).
. In the past, it was only possible to obtain grape juice during the grape harvest. Since last season’s wine would have already been used up and it would take another forty days to prepare wine from the new crop, the Sages permitted making kiddush on grape juice (BB 97b; SA 272:2). This is be-di’avad, especially when it comes to the Seder, where reciting the Hagada joyfully is an integral part of the institution. This argument is also advanced in Mikra’ei Kodesh 2:35, although in the notes on p. 130 the author advocates that women may fulfill the mitzva using grape juice. He argues that the reason for using intoxicating wine is to fulfill the mitzva of rejoicing on Yom Tov. Pesaĥim 109a states: “Every person must rejoice during the festival… men with what is appropriate for them – with wine, and women… in Babylonia with dyed clothing and in Eretz Yisrael with pressed linen clothing.” SA 529:2 and BHL ad loc. rule that, indeed, the joy of wine relates primarily to men.
Nevertheless, the most straightforward understanding of this mitzva requires women to drink the four cups of wine just like men, as “they too participated in that miracle” (Pesaĥim 108b). Until recent generations, this was the common practice of women. Nevertheless, intoxication is more disgraceful for women than for men (Ketubot 65a), so women concerned about intoxication may mix more grape juice into their wine.