Pesachim 108B

שאף הן היו באותו הנס.

As they too were included in that miracle of the Exodus, they are therefore obligated to participate in the celebration.

אמר רב יהודה אמר שמואל: ארבעה כוסות הללו צריך שיהא בהן כדי מזיגת כוס יפה. שתאן חי ⁠— יצא. שתאן בבת אחת ⁠— יצא. השקה מהן לבניו ולבני ביתו ⁠— יצא.

Rav Yehuda said that Shmuel said: These 4 cups must contain enough undiluted wine to allow for diluting a significant cup. In talmudic times, people would not drink pure wine. They would dilute it with water, generally adding 3 times as much water as wine. If one drank them undiluted, he has fulfilled his obligation. If one drank them all at once, i.e., he poured all 4 cups of wine into one large cup and drank it, he has fulfilled the obligation. If one gave his sons or the members of his household to drink from them, he has nevertheless fulfilled the obligation.

שתאן חי יצא, אמר רבא: ידי יין ⁠— יצא, ידי חירות ⁠— לא יצא.

The Talmud now addresses each of these rulings of Shmuel in turn. Shmuel said that if one drank them undiluted he has fulfilled his obligation. Rava said: He has fulfilled the obligation to drink the 4 cups of wine, but he has not fulfilled the obligation to drink in a way that expresses freedom, which is the preferable way to fulfill the mitzva, as aristocrats do not drink undiluted wine.

שתאן בבת אחת, רב אמר: ידי יין ⁠— יצא, ידי ארבעה כוסות ⁠— לא יצא. השקה מהן לבניו ולבני ביתו ⁠— יצא, אמר רב נחמן בר יצחק: והוא דאשתי רובא דכסא.

If one drank the 4 cups all at once, Rav said that he has fulfilled the obligation to drink wine as an expression of rejoicing on the Festival, but he has not fulfilled the obligation to drink 4 cups, which requires 4 distinct cups, each drunk separately. Shmuel also stated that if one gave his sons or the members of his household to drink from them, he has nevertheless fulfilled his obligation. Rav Naḥman bar Yitzḥak said: And this is the case only if he himself drank the majority of the cup.