My question is somewhat related to the post, Was the cave of Abraham in Shechem or Hebron?
However, in that post, the question revolved around whether the Patriarchs were buried in Hebron or Shechem. I don't want to argue about that point, and my question, although based on the same text, is on a different matter.
In Acts 7:15-16, Stephen claims that Abraham bought a tomb in Shechem where (at least) the Patriarchs are buried. Now, Genesis 33:19 and Joshua 24:32 make it clear that Jacob bought a piece of land in Shechem, where Joseph's remains were buried. However, the Old Testament has no account of Abraham's buying a tomb in Shechem. This leads me to the specific question: Supposing that the passage quoted from the Acts does reflect Stephen's words, where did Stephen get the information that Abraham bought a tomb at Shechem?