Throughout the Bible the concept of the false prophet is found. In the Old Testament this person was one who -
1. prophesied from their own imagination, or heart, instead of saying what God instructed
2. prophets of another God
3. prophets who would only prophesy when paid to do so
4. prophets whose words went against the words of God
In the New Testament, there is also the term 'false teachers' and these referred to the people who went about the emergent church and preached 'another gospel' (such as Gnosticism or any of the known heresies). Sometimes these were Jewish-Christians who wanted the church to retain the laws and rituals of Judaism. Sometimes these were individuals who taught something that did not follow the teachings of Jesus or the Apostles. Sometimes these were followers of pagan Gods who wanted to draw the Christians into, or back into, the pagan rituals.