A phrase from one of the parables of Jesus; he compares the journey to heaven to a search for fine pearls conducted by a merchant, “who, when he had found one pearl of great price, went and sold all that he had, and bought it.”
Note: The expression has come to mean anything that is very valuable. For example, Hester Prynne, in The Scarlet Letter, who gave birth to a daughter following an act of adultery that destroyed her honor, named the child Pearl, because she had given up all that she had in bearing the child.