Library Flavius Josephus Antiquities of the Jews, Book I
Book I, Chapter 14: Concerning Sarah Abraham's Wife; And How She Ended Her Days.
Now Sarah died a little while after, having lived one hundred and twenty-seven years. They buried her in Hebron; the Canaanites publicly allowing them a burying-place; which piece of ground Abraham bought for four hundred shekels, of Ephron, an inhabitant of Hebron. And both Abraham and his descendants built themselves sepulchers in that place.
English translation by William Whiston (1737). Public domain. Digital text via Project Gutenberg.