Long, long before Jesus warned that false prophets would arise during our time (Matthew 24:11, 24) — and long, long before the apostle Peter warned about the same threat to true Christian believers (2 Peter 2:1-2) — there had been many false prophets in Israel (and in the world, for that matter).
“But there were false prophets also among the people [the ancient nation of Israel] even as there will be false teachers among you [God’s Church], who will secretly bring in destructive heresies, even denying the Lord who bought them, and bring on themselves swift destruction. And many will follow their destructive ways, because of whom the way of truth will be blasphemed. By covetousness they will exploit you with deceptive words; for a long time their judgment has not been idle, and their destruction does not slumber” (2 Peter 2:1-5, NKJV throughout, unless otherwise stated).