By way of permission (kata sungnōmēn). Old word for pardon, concession, indulgence. Secundum indulgentiam (Vulgate). Only here in N.T., though in the papyri for pardon. The word means “knowing together,” understanding, agreement, and so concession.
Not of commandment (ou kat' epitagēn). Late word (in papyri) from epitassō, old word to enjoin. Paul has not commanded people to marry. He has left it an open question.