The oneness or unity of the Bible is a miracle. It is a library of 66 books, written by over 35 different authors in a period of approximately 1,500 years. Represented in the authors is a cross-section of humanity, both educated and uneducated, including: kings, fishermen, public officials, farmers, teachers, and physicians. Included in the subjects are religion, history, law, science, poetry, drama, biography, and prophecy.
Yes, its various parts are harmoniously united as the parts that make up the human body. For 35 authors, with such varied backgrounds, to write on so many subjects over a period of 1,500 years in absolute harmony, is a mathematical impossibility. It could not happen. Then how do we account for the Bible? The only account or explanation is this: some were moved by the Holy Spirit and spoke from God. See 2 Peter 2:21.