Old Testament Canon
The books that are considered to be part of Scripture are called canonical, or said to be a part of the canon, authoritative in matters of faith and doctrine. The term canon is derived from a Greek word meaning "a rule" or "measuring rod." A canon is a list to which other books are compared and by which they are measured.
The criteria for selecting the books in the Old Testament canon had to do with their worth in the religion of the Jewish nation. Jews call their 39 books of Scripture the Tanakh, an acronym formed from the first letters of Torah (Law), Naviim (Prophets), and Kethubim (Writings). These are known as the "Law of Moses, the Prophets, and the Psalms" in Luke 24:44.
For a thousand years, from Moses to Malachi, the Jewish religion existed wthout a closed canon. The people of the Old Testament didn't have the entire 39 books of the Old Testament, and it is uncertain just when the canon was closed.
The books of the Old Testament were originally divided into 24, according to the testimony of early Hebrew tradition. The Talmud, rabbinic literature, and probably the book of 4 Esdras speak of an arrangement which included 5 books of the Law, 8 of the prophets, and 11 of the Writings.
Of these, the one most important to the Israelites has always been the Law, also known as the Pentateuch, referring to 5 scrolls in one case (Genesis, Exodus, Leviticus, Numbers, and Deuteronomy). The second section, the Prophets, includes 4 historical books (Joshua, Judges, Samuel, and Kings), the books of the 3 major prophets (Isaiah, Jeremiah, and Ezekiel), and the books of the 12 minor prophets (Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habbakuk, Zephaniah, Haggai, Zechariah, and Malachi). The last section, known as the Writings, are subdivided into the "Wisdom Writings" (Psalms, Proverbs, Job, the Song of Songs, Lamentations, and Ecclesiastes), and the "Historical Writings" (Esther, Daniel, Ezra, Nehemiah, and Chronicles).