He is simply repeating what the Instruction already says. And, in the process, affirming other direct implications:
- the wife does not have authority to "put away" (and thus, not 'divorce', either!) her husband.
- She is not to leave (abandon) the marriage.
- Still, rebellion exists. Shaul/Paul acknowledges that.
- So, IF she leaves anyway - she STILL HAS A LIVING HUSBAND. She must not thus commit adultery.
- The husband (as we have discussed) MAY (for some* presumed 'unclean-ness') put away his wife, but should not.
What follows, logically, since he is not bound to having only one anyway: he may take another wife, particularly in her absence.
Thus follows what I consider on of three potential polygyny 'mandates' in Scripture. What if she returns?
Matthew 5:31-32 is not an "exception" for adultery in the sense generally taught by the twisters. It MUST BE UNDERSTOOD in the context of what He just said, as was DEMONSTRATING:
He was not changing "one yod or tiddle" of His Written Word.
So, if she committed adultery - she is
already an adulterer, and (were he inclined, see Numbers 5 et al) deserving of death. He COULD 'put her away' without so much as the clothes on her back. Anything else is 'grace' on his part.
And Shaul does not always need to repeat things His Master already taught. Often what his letters accomplish is "midrash" (a Hebrew term describing discussion or elaboration, as a method of teaching).
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* Note: I chose not to use 'nakedness' in this context, given confusion in English. Shouldn't it be OK for her to get naked for her husband? This thus must mean something a bit different...