{Only} (ei m(885c)). This use of ei m(885c) as an elliptical
condition is very common ( 7:5  Ga 1:7,19  Ro 14:14 ), "except
that" like pl(886e). Paul gives a general principle as a limitation
to what he has just said in verse  15 . "It states the general
principle which determines these questions about marriage, and
this is afterwards illustrated by the cases of circumcision and
slavery" (Robertson and Plummer). He has said that there is to be
no compulsory slavery between the believer and the disbeliever
(the Christian and the pagan). But on the other hand there is to
be no reckless abuse of this liberty, no license. {As the Lord
hath distributed to each man} (hekast(9369) h(9373) memeriken ho
kurios). Perfect active indicative of meriz(935c), old verb from
meros, apart. Each has his lot from the Lord Jesus, has his
call from God. He is not to seek a rupture of the marriage
relation if the unbeliever does not ask for it. {And so ordain I}
(kai hout(9373) diatassomai). Military term, old word, to arrange
in all the churches (distributed, dia-). Paul is conscious of
authoritative leadership as the apostle of Christ to the
Gentiles.