Four connected expressions of freedom
בין הכוסות הללו, אם רוצה לשתות, ישתה. בין שלישי לרביעי, לא ישתה
Between [the first and second, or second and third] cups, if one wants to drink, they may. Between the third and fourth cup, don’t drink [anything]
Our Sages enacted that we drink four cups of wine at the Seder, at different points of significance. One we drink for Kiddush, like any other Yom Tov. One we drink after finishing “Maggid”, the main part of the Haggadah, where we tell over the Exodus story. One we drink after saying Birkas HaMazon, the Grace after meals. The final cup we drink after finishing Hallel, Psalms of praise to Hashem for redeeming us. Our Sages specified certain rules for how to drink the cups, and in what manner. They specified an interesting rule. One is allowed to drink as much as they want between any of the first three cups. However, between the third and fourth cup, consuming any beverage is forbidden. Why would this be?
One simple reason is that by that point in the Seder, it’s already been a long night. The person has consumed three cups of wine. If they would be allowed to drink as they please, they may further consume alcoholic beverages. They may become intoxicated, and be unable to finish the Seder the way they’re supposed to. To prevent such a situation, the Sages said not to drink anything until the fourth cup. Another explanation is that before the meal and throughout, drinking wine can add to a person’s appetite. Therefore, any additional drink may simply be looked at as part of the meal. However, after the meal is over and the person drinks the third cup, there’s no need anymore to increase one’s appetite. Why then are they drinking wine? Any additional cup of wine could then appear like it’s one of the special cups of the Seder. Since there are supposed to be four cups and no more, the Sages saw fit to forbid any drinking, to avoid this concern from occurring.
While these explanations are more in line with the simple intent of the Sages, perhaps a more subtle explanation can be suggested. If we were to take a poll of worldwide Jewry and were to ask them their feelings about the four cups, there would probably be a unanimous response. The first cup is exciting, as it sets the tone for the evening. The second cup is inspiring, as it concludes the incredible story of the Exodus. The third cup is decent, as it marks a fitting end to the meal. If we were to ask people, they would probably say they could do without the fourth cup. After all that wine and matzah, most people probably had enough.
One of the explanations for why the Sages instituted four cups of wine at the Seder is to correlate to the four expressions of redemption that appear in the Torah: והוצאתי אתכם, I took you out, והצלתי אתכם, I saved you, וגאלתי אתכם, I redeemed you, ולקחתי אתכם, I took you [for Me to be a nation]. If we were to ask people, the first three would definitely be relatable concepts. Independence, security, freedom. These values resonate with people. They’re naturally easy to accept. The last expression of freedom is a harder pill to swallow. Obedience, subservience, and loyalty to Hashem are things people are naturally inclined to avoid. We like our independence, and have a hard time with authority.
The Sages forbidding drinking between the third and fourth cup was to teach us not to make a separation. Sure, freedom and independence are wonderful, but they’re meaningless without Hashem in our lives. The fourth cup, which represents us being Hashem’s nation, not just any nation, goes hand in hand with the other cups. The other cups have no danger if they’re disconnected, so they allowed us to drink as we please. To connect the fourth cup to the others, they forbade drinking anything else.
Good Shabbos and Chag Sameach!
 See Rashbam to Pesachim 108a s.v. בין כוסות הללו. For some reason Rashi ad. loc. only mentions between the first and second cup, and Rashbam to ibid 117b s.v. says between the first two cups and the last two cups (essentially meaning, between the second and third cup)
 Pesachim 10:7
 Yerushalmi Pesachim 10:6, brought by Rashbam loc. cit.
 Rashbam to Pesachim 108a loc. cit. It’s interesting that he only brings this explanation there, and not on the Mishnah that says this law
 Bereishis Rabbah 88:5 and Yerushalmi Pesachim 10:1, cited by Rashi and Rashbam to Pesachim 99b s.v. ארבע כוסות
 Exodus 6:6
 Ibid v. 7
 It’s interesting then that the fourth expression of redemption is separated from the others in its own verse