The Council of Rome in AD 382 formally canonized these seven “deuterocanonical” books along with the rest of the OT and NT as we know it.
Martin Luther removed these seven books from the OT because first century Rabbinical Jews had previously rejected them. Protestants call them the “Apocrypha” meaning “hidden” books. First century Jews who denied that Jesus was the Messiah rejected these seven books because of their emphasis on the Messiah and the resurrection.
However, the New Testament actually refers to the seven “extra” deuterocanonical books, which means that the NT authors approved of these seven books. For example:
o Heb 11:35 refers to 2 Mac 6:18-7:42
o 1 Pet 1:6-7 refers to Wisdom 3:5-6
o Rom 1:18-32 refers to Wisdom 13:1-9
The Greek version of the OT called the “Septuagint” contained the deuterocanonicals and the Septuagint is frequently quoted by the NT authors: Is 7:14 - Mt 1:23; Is 40:3 - Mt 3:3; Joel 2:30-31 - Acts 2:19-29; Ps 95:7-9 - Heb 3:7-9.