1 Corinthians 6:16

Or don’t you know that he who unites himself with a prostitute is one with her in body? For it is said, “The two will become one flesh.”

Note Genesis 2:24 (see also LXX)

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

Or don’t you know that he who is joined to a prostitute is one body? For, “The two”, he says, “will become one flesh.”

Or know ye not that he that is joined to a harlot is one body? for, The twain, saith he, shall become one flesh.