Why does Jephthah repeat many parts of what his daughter said?
Judges 11:38 (ESV)
38So he said, “Go.” Then he sent her away for two months, and she departed, she and her companions, and wept for her virginity on the mountains.
In those days, repetition helped both the speaker and the hearer to take in elements of the story and remember them. Moreover, it works as an emphasis. It prepares for Judges 11:40 which explains that this is the origin of a custom.
38 So he said, “Go.” Then he sent her away for two months, and she departed, she and her companions, and wept for her virginity on the mountains.