The false teaching that had entered the church had produced some inappropriate behavior in some. Paul wrote what to do about this situation to guide the Thessalonians in bringing their behavior as well as their belief back into conformity with God's will.
"As important as it is to identify the cause and nature of the problem behavior addressed in vv. 6-15, we should not ignore the fact that our passage both begins (v. 6) and ends (vv. 14-15) with exhortations, not to the idle but to the rest of the church. The admonition addressed directly to those Christians who were living improperly (v. 12) is, in fact, rather brief."67