Our Old Testament consists of the holy scriptures of Judaism, which makes it clear that we as Christians cannot separate ourselves from our Jewish roots without losing everything—and that we worship the same God as devout Jews.

Most of these writings, called the Tanakh in Judaism, were written in Hebrew, with only parts of the Book of Daniel and the Book of Ezra available in Aramaic. Aramaic, also a Semitic language, is closely related to Hebrew and served as the lingua franca throughout the Near East since at least the Persian rule around 500 BC.

The division of the Jewish Tanakh differs from that of our Old Testament. While Christianity primarily used a chronological arrangement, the rabbis divided the Tanakh thematically into three main parts, consisting of a total of 24 books:

1. The Law – Hebrew Torah (meaning guidance): the five books of Moses
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2. The Prophets – Hebrew Nevi’im, 8 books, here first the former or early prophets:
   Joshua, Judges, Samuel, and Kings
   then the latter prophets: Isaiah, Jeremiah, Ezekiel
   and finally the so – called 12 minor prophets, which in Judaism are counted as a single book.
   ^.
3. The Writings, also called Psalms – Hebrew Ketuvim, 11 books
   a) the 3 poetic books: Psalms, Proverbs, Job
   b) the 5 scrolls (Hebrew Megilloth): Song of Solomon, Ruth, Lamentations of Jeremiah, Ecclesiastes, Esther
   These five books are also called festival scrolls because each one is read aloud on a specific Jewish holiday to this day.
   c) 3 prophetic-historical books: Daniel, Ezra-Nehemiah, Chronicles

The term Tanakh, as the name of the Hebrew Bible, is composed of the first letters of these three parts—Torah, Nevi’im, Ketuvim.

In the first century, during the lifetime of the apostles, the Jewish historian Josephus counted only 22 books in the Tanakh, corresponding to the 22 letters of the Hebrew alphabet.
Originally, the books of Judges and Ruth, as well as Jeremiah and Lamentations, were also combined into one book each.

However, the three-part structure of the Tanakh already existed at the time of Jesus, who himself refers to the Hebrew Bible in Luke chapter 24, verse 44 as “the Law of Moses and the Prophets and the Psalms.”

The extent to which Jewish writings have been incorporated into our Old Testament varies depending on the Christian denomination.

While the Reformers, and thus Protestantism, divided the 24 books of the Tanakh into 39 books, the Orthodox and Catholic Churches added further books (the so-called Apocrypha) from more recent copies of the Septuagint.
Thus, the Catholic Bible canon comprises 46 books and the Orthodox canon, depending on the church organization, up to 51 books in the Old Testament.

The Septuagint (Latin for seventy, because according to legend, 72 scholars translated the Torah in 72 days) is the first translation of the Hebrew texts into Greek. It was begun around 250 BC in Alexandria, Egypt, for the Jewish population of the Greek-speaking Mediterranean region.

Because these writings lack references to the redemptive work of Jesus Christ and the work of the Holy Spirit, among other things, most theologians do not recognize them as inspired by God, as the rest of our Bible is, but rather consider them to be historical books of Judaism.
Another indication of their non-authenticity is that although the apostles, and even our Lord Jesus Christ himself, very often quote from the canonical books of the Old Testament, nowhere in the New Testament is a single passage from any of the apocryphal writings quoted.

500 years ago, Martin Luther commented on these apocryphal writings, which means hidden, occult, secret, and which are also called late writings:
“These are books that are not considered equal to Holy Scripture, but are nevertheless useful and good to read.”

But even in Judaism itself, these apocryphal books never belonged to the canon of the sacred writings of the Tanakh, but were merely added to later copies of the Greek translation.