230. "if he divorces her (for the third time), she shall not be lawful to him
thereafter, until she marries another husband;
and if he (the latter) divorces her,
then it is no sin on (either of) them to return to each other (by marriage),
if they think that they can keep allah's bounds.
those are allah's limits; he makes them clear to a people who know.

occasion of revelation
once, at the time of prophet of islam (p.b.u.h.), a woman came to
him and said she had been the spouse of her cousin by the name of
rifa`ah, who divorced her thrice. after that, she married a man named
`abd-ur-rahman, but he, before any sexual relations with her, divorced
her, too. then, she asked the prophet (p.b.u.h.) whether she could
return to her first husband.

the messenger of allah (p.b.u.h.) did not agree and said that her
marriage with that first husband was right if she had sexual intercourse
with her new husband. the above verse was revealed.

commentary:
in the commentary of the previous verse this fact was briefly
referred to that: after the second divorce, the couple should either
follow the path of peace and kindness, or separate from each other for
ever.

the verse under discussion is counted as a note, indeed, added to
that ordinance. it says:

" if he divorces her (for the third time), she shall not be lawful to him
thereafter, until she marries another husband;
and if he (the latter) divorces her, then it is no sin on (either of) them
to return to each other (by marriage), if they think
that they can keep allah's bounds.

messages
1- men should not misuse their conjugal rights. they ought to
know that they are not free and authoritative upon their wives forever
in this regard.
it is narrated from imam rida (a.s.) who said: " do not take divorce
light, and do not cause your wives to incur a loss."
20

2- not every one knows the secrets and the wisdom of the divine
laws, therefore some people, maybe, look at these instructions
surprisingly, while the secrets of them are clear for those who have
insight. common people often see the apparent of these instructions,
but the cognizant recognize the spirit and the depth of them.
3- muslims should know that the limits of allah are not liable
only to prayers, alms, hajj, and holy war. observing the family affairs
are the limits of allah, too.

"...those are allah's limits; he makes them clear to a people who know."