After Birkat Ha-mazon, we drink the third cup of wine and then pour the fourth cup, over which we recite Hallel and “the Great” Hallel (“Hallel Ha-gadol”).
Before Hallel we recite the paragraph “Shefokh Ḥamatkha” (“Pour Your wrath upon the nations that know You not…”). Some have the custom to open the door at this point, to demonstrate that, on this night, we are protected against destructive forces and not afraid of our enemies. By virtue of this faith, the Mashi’aḥ (Messiah) will come and pour out his wrath upon the wicked enemies of Israel (Rema 480:1). Some have a custom to stand while reciting Shefokh Ḥamatkha (AHS ad loc., and this was the practice of Rav Kook). After reciting Shefokh Ḥamatkha, we close the door.
We then continue with the second part of Hallel (see above, section 20). There is a mitzva to recite certain verses (Tehilim 118:1-4, 24-25) in reader and response format; the Seder leader recites the verse first, and the remaining participants respond. Le-khatḥila there is a mitzva to ensure that three adults are present in order to recite the verses in this manner (Rema 479:1). However, an individual fulfills the mitzva even by reciting Hallel alone. If only two people are present, they should recite the verses together (MB 479:10-11).
After this, we recite the Great Hallel (chapter 136 of Tehilim) followed by Nishmat Kol Ḥai (“The Soul of All Life”) and the concluding berakha. There are different opinions regarding the formula of the concluding berakha: Sephardim close with the paragraph “Yehallelukha,” which concludes the normal recitation of Hallel. Ashkenazim close with “Yishtabaḥ,” which concludes the psalms of praise recited at Shaḥarit (see section 31 above, where we learned that it is better to complete this berakha by midnight). Following this, we sing various songs composed in the era of the Rishonim.
Simplicity dictates that the fourth cup should be drunk right after the concluding berakha of Hallel, which also concludes the Seder that was instituted by the Sages in the times of the Mishna, and that the songs and poems that follow are merely a custom. Nevertheless, some drink the fourth cup after singing a few of these additional songs, so that they too are sung over a cup of wine and are thus included in the Seder (see MB 480:6). Each family should continue its own tradition.
Sephardic custom is not to recite “ha-gefen” before the fourth cup, whereas Ashkenazic custom is to recite it (see section 21 above). After the fourth cup, the berakha aḥarona of “Al Ha-gefen” is recited.