{As his custom was} (kata to ei(9374)hos t(9369) Paul(9369)). The same
construction in  Lu 4:16  about Jesus in Nazareth (kata to
ei(9374)hos aut(9369)) with the second perfect active participle neuter
singular from eth(935c). Paul's habit was to go to the Jewish
synagogue to use the Jews and the God-fearers as a springboard
for his work among the Gentiles. {For three Sabbaths} (epi
sabbata tria). Probably the reference is to the first three
Sabbaths when Paul had a free hand in the synagogue as at first
in Antioch in Pisidia. Luke does not say that Paul was in
Thessalonica only three weeks. He may have spoken there also
during the week, though the Sabbath was the great day. Paul makes
it plain, as Furneaux shows, that he was in Thessalonica a much
longer period than three weeks. The rest of the time he spoke, of
course, outside of the synagogue. Paul implies an extended stay
by his language in  1Th 1:8 . The church consisted mainly of
Gentile converts ( 2Th 3:4,7,8 ) and seems to have been well
organized ( 1Th 5:12 ). He received help while there several
times from Philippi ( Php 4:16 ) and even so worked night and day
to support himself ( 1Th 2:9 ). His preaching was misunderstood
there in spite of careful instruction concerning the second
coming of Christ ( 1Th 4:13-5:5  2Th 2:1-12 ). {Reasoned}
(dielexato). First aorist middle indicative of dialegomai,
old verb in the active to select, distinguish, then to revolve in
the mind, to converse (interchange of ideas), then to teach in
the Socratic ("dialectic") method of question and answer (cf.
dielegeto in verse  17 ), then simply to discourse, but always
with the idea of intellectual stimulus. With these Jews and
God-fearers Paul appealed to the Scriptures as text and basis
(apo) of his ideas.