{Called to be an apostle} (kl(8874)os apostolos). Verbal
adjective kl(8874)os from kale(935c), without einai, to be.
Literally, {a called apostle} ( Ro 1:1 ), not so-called, but one
whose apostleship is due not to himself or to men ( Ga 1:1 ), but
to God, {through the will of God} (dia thel(886d)atos tou theou).
The intermediate (dia, duo, two) agent between Paul's not being
Christ's apostle and becoming one was God's will (	hel(886d)a,
something willed of God), God's command ( 1Ti 1:1 ). Paul knows
that he is not one of the twelve apostles, but he is on a par
with them because, like them, he is chosen by God. He is an
apostle of Jesus Christ or Christ Jesus (MSS. vary here, later
epistles usually Christ Jesus). The refusal of the Judaizers to
recognize Paul as equal to the twelve made him the more careful
to claim his position. Bengel sees here Paul's denial of mere
human authority in his position and also of personal merit:
_Namque mentione Dei excluditur auctoramentum humanum, mentione
Voluntatis Dei, meritum Pauli_. {Our brother} (ho adelphos).
Literally, the brother, but regular Greek idiom for our brother.
This Sosthenes, now with Paul in Ephesus, is probably the same
Sosthenes who received the beating meant for Paul in Corinth ( Ac
18:17 ). If so, the beating did him good for he is now a follower
of Christ. He is in no sense a co-author of the Epistle, but
merely associated with Paul because they knew him in Corinth. He
may have been compelled by the Jews to leave Corinth when he, a
ruler of the synagogue, became a Christian. See  1Th 1:1  for the
mention of Silas and Timothy in the salutation. Sosthenes could
have been Paul's amanuensis for this letter, but there is no
proof of it.