The third cup of wine represents God’s third declaration of redemption: וגאלתי / V'go'alti —“I will liberate you with an outstretched arm…” 

בָּרוּךְ אַתָּה יְיָ, אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם, בּוֹרֵא פְּרִי הַגָּפֶן:

Baruch atah, Adonai, eloheinu melech ha’olam, borei pri hagafen.

Blessed are you, Adonai our God, Ruler of the universe, creator of the fruit of the vine.

haggadah Section: Hallel
Source: Velveteen Rabbi's Haggadah for Pesach