II Corinthians 11:4 and 13-15

"For if he who comes preaches another Jesus whom we have not preached, or if you receive a different spirit which you have not received, or a different gospel which you have not accepted--you may well put up with it!"

"For such are false apostles, deceitful workers, transforming themselves into apostles of Christ."

"And no wonder! For Satan himself transforms himself into an angel of light."

"Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works."

(Paul here is telling the Corinthian church to beware of those who would confuse them with a differing gospel. Nowadays, so many churches and pastors are false apostles working on Satan's behalf, and not all of them even know they're doing wickedly! We need to be a light to the world, and show the true Gospel of Jesus Christ to all people. And don't let workers of deceit make you question the validity of the Bible.)