NET

16 Or do you not know that anyone who is united with a prostitute is one body with her? For it is said, “The two will become one flesh.”

Darby

16 Do ye not know that he [that is] joined to the harlot is one body? for the two, he says, shall be one flesh^D8262.

Darby Bible Notes

flesh - Lit. 'to (eis) one flesh.' In English 'shall' or 'shall become' is the nearest in sense. It corresponds to the Hebrew of Gen. 2.24. Eis is left out when he says 'one Spirit' in ver. 17. We are really 'one Spirit,' not two, with the Lord. But we cannot say, 'to' or 'for one flesh.' The two become so (i.e. 'one flesh') practically by their union; they are created individually. The union induces unity in the flesh; 'shall be,' or 'shall become' partly, though imperfectly, implies this. see Matt. 19.5. It is not 'shall be one Spirit.' but 'he is.' The Spirit which is in the Lord himself dwells in us, and is the living power of the new life.

KJV

16 What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh.