The third cup symbolizes the third expression of redemption: " Ve'ga'alti -- And I will redeem you with an outstretched arm and with great judgement" (Exodus 6:6-8). This refers to the splitting of the sea. Until the splitting of the sea, the Israelites feared that their Egyptian taskmasters would chase after them and re-enslave them. Only upon seeing the Egyptians dead on the seashore did they know that they were truly free; only then could they truly rejoice (and thus they sang the song at the sea). 

G-d's arm remains forever outstretched, for G-d is always protecting the people of Israel (R. Joseph Soloveitchik). As we are supposed to emulate G-d, we too must stretch out our arm and help protect those in need. 


haggadah Section: Bareich
Source: ArtScroll Chumash: The Stone Edition