{So then} (ara oun). Accordingly then. The illative ara
is supported (Ellicott) by the collective oun as in  1Th 5:6  Ga 6:10 , etc. Here is the practical conclusion from God's
elective purpose in such a world crisis. {Stand fast}
(st(886b)ete). Present imperative active of the late present
st(886b)o from hest(886b)a (perfect active of hist(886d)i). See on 气Th
3:8|. {Hold the traditions} (krateite tas paradoseis). Present
imperative of krate(935c), old verb, to have masterful grip on a
thing, either with genitive ( Mr 1:31 ) or usually the accusative
as here. Paradosis (tradition) is an old word for what is
handed over to one. Dibelius thinks that Paul reveals his Jewish
training in the use of this word ( Ga 1:14 ), but the word is a
perfectly legitimate one for teaching whether oral, {by word}
(dia logou), or written, {by epistle of ours} (di' epistol(8873)
h(886d)(936e)). Paul draws here no distinction between oral tradition
and written tradition as was done later. The worth of the
tradition lies not in the form but in the source and the quality
of the content. Paul in  1Co 11:23  says: "I received from the
Lord what I also handed over (pared(936b)a) unto you." He praises
them because ye "hold fast the traditions even as I delivered
them unto you." The {tradition} may be merely that of men and so
worthless and harmful in place of the word of God ( Mr 7:8  Col
2:6-8 ). It all depends. It is easy to scoff at truth as mere
tradition. But human progress in all fields is made by use of the
old, found to be true, in connection with the new if found to be
true. In Thessalonica the saints were already the victims of
theological charlatans with their half-baked theories about the
second coming of Christ and about social duties and relations.
{Which ye were taught} (has edidachth(8874)e). First aorist passive
indicative of didask(935c), to teach, retaining the accusative of
the thing in the passive as is common with this verb like _doce(935f)
in Latin and teach in English.