Titus 1:10-16 ~ 10- For there are many unruly and vain talkers and deceivers, specially they of the circumcision: 11- Whose mouths must be stopped, who subvert whole houses, teaching things which they ought not, for filthy lucre's sake. 12- One of themselves, even a prophet of their own, said, The Cretians are alway liars, evil beasts, slow bellies. 13- This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith; 14- Not giving heed to Jewish fables, and commandments of men, that turn from the truth. 15- Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled. 16 -They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate.
That statement is no more apparent than when we look at what is perpetrating and passing itself off to be the modern "church". I suppose it has always been like this. Early on Judaizers were trying to convert believers back into Jewish ritualism for salvation (Acts 15). Later gnostics such as Hymenaeus and Philetus who left the faith, tried to reinvent the teachings of Jesus and the Apostles claiming that either the resurrection had passed or that there was no physical or bodily resurrection because, according to them, the physical body was too evil to resurrect. (2 Tim. 2:18) False teachings were so prevalent until Apostle John warned that we should not "believe every spirit" but "try the spirit" whether it was of God. (1 John 4:1).