How to deal with counterfeits

Dr. Gray gave a talk to Margarat Nicholl Laird's graduating class at Moody Bible Institute in Chicago. Here is how she recounts it in her book, They Called Me MAMA, pp. 43-45:

Our class was a record class both in terms of number as well as in percentage of students who were to go to the foreign mission field.
"Recently," [Dr. Gray] said, "there has been a huge influx of counterfeit money in this country, enough so that the government has become alarmed and called in the FBI. To meet the demand for counterfeit-money agents, the FBI held a special six-week course to study the problem of counterfeit money."
Then, Dr. Gray paused. "Now, tell me, how many pieces of counterfeit money do you suppose those agents handled to become thoroughly acquainted with the problem?"
My classmates called out different numbers: "Twenty!" "Fifty!" "One hundred!" "Ten Thousand!" "A million!" All types of answers, small numbers, and fantastic numbers.
Dr. Gray listened and then spoke up: "Those agents never saw one piece of counterfeit money. These six weeks of study were for intensive training to know every grain, every thread, every picture, every number that was inherent in an authentic printed bill. In this way they would recognize good money immediately. The FBI knew that if these trainees were absolutely acquainted with the genuine article, they could immediately detect the unauthentic item.
"You young people are called of the living God to take the Gospel of the Lord Jesus Christ to the uttermost parts of the earth. You will find many strange new cultures. There is a great deal of devil worship. There is a great deal of fetishism, animism, and many other things that you will contact on the field. And I know many young people are tempted to study these things.
"God has given you the genuine thing. This is all He asks of you: Give out the Gospel of the Lord Jesus Christ. He'll take care of the counterfeits. He's the only One who can."
I never forgot that testimony! Today, almost fifty years later, I can look back and wholeheartedly support the idea in that statement.
I didn't realize how much it would mean to me. I've met missionaries who spent much time studying spiritism and animism. In fact, I know of missionaries who were brought back to the United States in straitjackets because they insisted on going to the woods to attend these devil worship services to get pictures and recordings to use on furlough.
I've learned that the devil, our enemy, is powerful, too. You can best resist him by having nothing to do with him.
Deal only with the genuine article. Look, find, and then hold onto the real thing: Jesus Christ.