Let us be on our guard against false doctrine. Unsound faith will never be the mother of really sound practice, and in these latter days, departures from the faith abound. See then that your loins be girded about with truth, and be very jealous of receiving anything which cannot be proved by the Bible.
Do not think for a moment that false doctrine will meet you face to face, saying, “I am false doctrine, and I want to come into your heart.” Satan does not go to work in that way. He dresses up false doctrine like Jezebel — he paints her face and attires her hair, and tries to make her like truth. Do not think that those who preach error will never preach anything that is true. Error would do little harm if that was the case. No! Error will come before you mingled with much that is sound and scriptural.
~ J.C. Ryle