As he prayed, he added a phrase to the traditional prayer, saying "Avinu Malkeinu" ("Our Father, Our King"). This phrase acknowledged G-d's Fatherly relationship with the Jewish people, while also recognizing His sovereignty and power.
As soon as Rabbi Akiva uttered these words, the skies darkened, and a healthy rain began to fall, ending the drought. The people were overjoyed, and the phrase "Avinu Malkeinu" became an integral part of Jewish liturgy, particularly during the High Holy Days.