Jacob had spoken to the people before. He had given them the same instructions that his father had given him. And he had spoken concerning "all things which are written, from the creation of the world." He had evidently told the people the story of the world, as we have it in Genesis, and of the dealings of God with his people, as recorded in other Scriptures. Those are the proper subjects of discourses at all times, in religious meetings. The Bible contains the word of God to man, as do the other sacred Scriptures.