Bibliomancy
Bibliomancy (Latin biblio, book) is divination by random opening of a sacred or revered book and interpreting the first passage read. Practice common in Antiquity with Homer (sortes Homericae), Virgil (sortes Virgilianae), and in the Christian Middle Ages with the Bible (sortes biblicae) and the works of Augustine.
Famous case
St. Augustine (Confessions, 397 AD) reports his conversion experience: he heard the voice "tolle, lege" (take, read), opened the Bible at random, and read Romans 13:13-14 — which transformed his life.