Note 8 at 1 Th. 3:5: Paul was very concerned about the Thessalonians' faith. Were they still fully trusting Christ or had the tempter been able to lure them away? Both Jesus and Paul spoke of a temporal faith that looked very much like the real thing but when times get rough these people fall away (Lk. 8:13; 1 Cor. 15:2). A committed faith is that which perseveres, will never give up, and will follow Christ no matter the cost (Mt. 19:27).

In 1 Corinthians 15:2 Paul described a faith that does not continue to follow Christ as a faith that is "vain." "Vain" means not yielding the desired outcome; unsuccessful. Satan was using persecution to try to snatch away the Word which was sown in the Thessalonians' hearts. The outcome that Paul was believing for was full Christian maturity. Anything else would not be considered a success by Paul. His preaching would have been in vain.