Answer by taking a quote from the following article:

Fiddler on the Roof is a musical with music by Jerry Bock, lyrics by Sheldon Harnick, and book by Joseph Stein, set in the Pale of Settlement of Imperial Russia in 1905. It is based on Tevye and his Daughters (or Tevye the Dairyman) and other tales by Sholem Aleichem. The story centers on Tevye, the father of five daughters, and his attempts to maintain his Jewish religious and cultural traditions as outside influences encroach upon the family's lives. He must cope both with the strong-willed actions of his three older daughters, who wish to marry for love - each one's choice of a husband moves further away from the customs of his faith - and with the edict of the Tsar that evicts the Jews from their village.

Months later, Perchik tells Hodel he must return to Kiev to work for the revolution. He proposes marriage, admitting that he loves her, and says that he will send for her. She agrees ("Now I Have Everything"). They tell Tevye that they are engaged, and he is appalled that they are flouting tradition by making their own match, especially as Perchik is leaving. When he forbids the marriage, Perchik and Hodel inform him that they do not seek his permission, only his blessing. After more soul searching, Tevye relents - the world is changing, and he must change with it ("Tevye's Rebuttal"). He informs the young couple that he gives them his blessing and his permission. Tevye explains these events to an astonished Golde. "Love," he says, "it's the new style." Tevye asks Golde, despite their own arranged marriage, "Do You Love Me?" After dismissing Tevye's question as foolish, she eventually admits that, after 25 years of living and struggling together and raising five daughters, she does. Meanwhile, Yente tells Tzeitel that she saw Chava with Fyedka. News spreads quickly in Anatevka that Perchik has been arrested and exiled to Siberia ("The Rumor/I Just Heard"), and Hodel is determined to join him there. At the railway station, she explains to her father that her home is with her beloved, wherever he may be, although she will always love her family ("Far From the Home I Love"). Time passes. Motel has purchased a used sewing machine, and he and Tzeitel have had a baby. Chava finally gathers the courage to ask Tevye to allow her marriage to Fyedka. Again Tevye reaches deep into his soul, but marriage outside the Jewish faith is a line he will not cross. He forbids Chava to speak to Fyedka again. When Golde brings news that Chava has eloped with Fyedka, Tevye wonders where he went wrong ("Chavaleh Sequence"). Chava returns and tries to reason with him, but he refuses to speak to her and tells the rest of the family to consider her dead. Meanwhile, rumors are spreading of the Russians expelling Jews from their villages. While the villagers are gathered, the Constable arrives to tell everyone that they have three days to pack up and leave the town. In shock, they reminisce about "Anatevka" and how hard it will be to leave what has been their home for so long. As the Jews leave Anatevka, Chava and Fyedka stop to tell her family that they are also leaving for Krakow, unwilling to remain among the people who could do such things to others. Tevye still will not talk to her, but when Tzeitel says goodbye to Chava, Tevye prompts her to add "God be with you." Motel and Tzeitel go to Poland as well but will join the rest of the family when they have saved up enough money. As Tevye, Golde and their two youngest daughters leave the village for America, the fiddler begins to play. Tevye beckons with a nod, and the fiddler follows them out of the village.

Why did Perchik have to send for Hodel?
Hodel he must return to Kiev to work for the revolution.