A witness may be asked, while under examination, whether any contract, grant or other disposition of property, as to which he or she is giving evidence, was not contained in a document, and if he or she says that it was, or if he or she is about to make any statement as to the contents of any document, which, in the opinion of the court, ought to be produced, the adverse party may object to that evidence being given until the document is produced, or until facts have been proved which entitle the party who called the witness to give secondary evidence of it.

Explanation."A witness may give oral evidence of statements made by other persons about the contents of documents if the statements are in themselves relevant facts.