We also add what is mentioned in the Book of Revelation about Balaam's perversion, the details of which are not recorded in the Book of Numbers (Num.24: 25). In the Book of Revelation, it is written: "...because you have there those who hold the doctrine of Balaam, who taught Balak to put a stumbling block before the children of Israel, to eat things sacrificed to idols, and to commit sexual immorality" (Rev.2: 14). In the Book of Numbers it is mentioned that the people did that but not that it was Balaam's doctrine. So probably St. John the Visionary who wrote the Book of Revelation knew it through Tradition.