[2:230] If he divorces her, she shall not be lawful to him after that, until she marries another husband. If he divorces her, then neither of them would be at fault to return to each other,
A man finds it unbearable that his wife should marry another, so [God] prevents him from choosing separation with the intention of keeping her from remarrying. He explains that she will not be lawful for him once he has separated from her until she does what he would find unbearable, and that is a second marriage. So he will be cautious, as much as he is able, in [initiating] divorce. Then He said: If he divorces her, meaning the spouse, then neither of them would be at fault to return to each other, meaning her remarrying the first husband.
The allusion in it is that love's capture of the heart makes the endurance of every misery easy, for if after separating, the spouses feel regret for their lost union, and then the greatest remorse, there is no fault in their returning to each other. The woman in this circumstance is as if she is protected from the first husband by the place of the second husband while the husband is like one who has brought this on himself in permitting that.
[2:230 cont'd] if they think that they will maintain God's bounds. Those are God's bounds, which He makes clear to a people who have knowledge.
It means that when they know their need for each other as companions, they will not separate a second time. The one who spoke for them said:
I swore that if I met you
one more time,
I would never again separate from you
a second time.