Romans 16:19

For your obedience is come abroad unto all men. I rejoice therefore over you: but I would have you wise unto that which is good, and simple to that which is evil.

The threat of evil teachers and their seductive operations was pointed out by Christ himself (Matthew 7:15-23), and the Saviour's description of such persons is still the fountain source of the true knowledge concerning them. They are wolves in sheep's clothing, being recognizable principally by their fruits. The minister, or other teacher, who scatters the flock is a wolf, regardless of his pretensions. His sheepskin garb and pretended piety cannot disguise his true status as an enemy. Paul, of course, rejoiced that until the time then present, the Roman leadership had preserved harmony and unity among the Christians; but, by Paul's warning here, he prophetically alerted them to certain danger ahead. Paul was careful, in giving such an alert, not to insinuate that the false teachers had already arrived there, hence the first clause of this verse; but it would have been folly not to warn them.

Simple unto that which is evil ... seems a little ambiguous as applied to Paul's argument here and has been explained in various ways; but its manifest reference to a desired reaction against the wiles of false teachers gives a clue to the false teacher's modus operandi, which was invariably grounded in a pretended superiority of knowledge and intelligence. Their views were always "advanced," allegedly, and were represented to be very learned and complicated, and thus contrasting dramatically with the great simplicities of the true religion of Christ. As Paul wrote:

But I fear, lest by any means, as the serpent beguiled Eve in his craftiness, your minds should be corrupted from the simplicity and purity that is toward Christ (2 Corinthians 11:3).

The boldness of the false teacher is always evident in his blunt rejection of valid truth coupled with an arrogant charge of simple-mindedness against those who hold and believe it. Very well, Paul seemed to say in this place, I want you to stay simple with reference to the so-called erudition of the false teacher!

The following verse, with its reference to bruising Satan under their feet, dramatically recalls that scene in Eden where God foretold such a bruising, a thing also clearly in Paul's mind in the verse just cited, above, and in which primeval event there existed the same element of the false wisdom still being promised by Satan and his workers. Satan promised Eve that she should be "as God, knowing good and evil" (Genesis 3:5); but the unfortunate mother of all living would have been wiser to have remained simple to the wisdom Satan offered. This is the thrust of Paul's word here.