Q. When did Catholics add books to the Bible?
A. They never did. The Jews and the Protestants removed books from the OT. The Catholic Church simply received the Septuagint version of the Hebrew scriptures, from the Jews, at the time of Christ. This became known as the Old Testament. 70 years later, the Jews removed 7 Old Testament books from the Septuagint. The reason given for this was that they could no longer find those books in Hebrew.
Interestingly some of these books were being used to good advantage to make converts among the Jews. For example:
This passage prophesies and describes the attitude of the enemies of Jesus hundreds of years before His birth:
The Book of Wisdom
The wicked said among themselves, thinking not aright:
Let us beset the just one, because he is obnoxious to us; he sets himself against our doings, Reproaches us for transgressions of the law and charges us with violations of our training. He professes to have knowledge of God and styles himself as a child of the Lord. To us he is the censure of our thoughts; merely to see him is a hardship for us, Because his life is not like other men’s and different are his ways. He judges us debased; he holds aloof from our paths as from things impure. He calls blest the destiny of the just and boasts that God is his Father. Let us see whether his words be true; let us find out what will happen to him. For if the just one be the son of God he will defend him and deliver him from the hand of his foes. With revilement and torture let us put him to the test that we may have proof of his gentleness and try his patience. Let us condemn him to a shameful death; for according to his own words, God will take care of him. These were their thoughts, but they erred, for their wickedness blinded them, and they knew not the hidden counsels of God neither did they count on a recompense of holiness nor discern the innocent souls’ reward.
Prayers for the dead and support for Purgatory (since people in Heaven don’t need prayers and people in Hell can’t be helped by prayers) are scriptural based on the following passage.
II Maccabees 12:44-45
For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead.
But if he was looking to the splendid reward that is laid up for those who fall asleep in godliness, it was a holy and pious thought. Therefore he made atonement for the dead, that they might be delivered from their sin.
In 1529, Martin Luther removed the same 7 books from the Catholic Old Testament, that the Jews had removed1400 years earlier. Luther also removed 4 New Testament books (Hebrews, James, Jude, and Revelation) that did not agree with his theology, for his German translation. These books were removed from their original place in the order of the books and placed together at the end of the Bible. In later editions, he was persuaded to return the New Testament books to to their proper position in his translation of the Bible. Today Protestant Bibles don’t contain 7 Old Testament books at all.
Q. What is the Septuagint?
A. In the centuries leading up to the birth of Christ the Jews were living all over the known world. Greek was the language of commerce and scholarship. Over time it became harder and harder to maintain a wide knowledge of Hebrew among the Jews because more and more were speaking only Greek. The Jews in Alexandria set about to make a Greek translation of the Hebrew scriptures. This translation was completed between 250-125 BC by 70 Jewish scholars. Septuagint means 70 in Latin.
Scholars are certain that Jesus and the early Christians accepted the Septuagint version of the Old Testament because etymological studies of 300 quotes from the Old Testament made by the New Testament writers can be traced back to the Septuagint version. There are also OT quotes that can be traced back to the Hebrew OT but these are far fewer in number. So, if Jesus had rejected the Septuagint the New Testament writers seemed to know nothing about it since they all used it quite freely.