Tafsir Al-Jalalayn: At-Talaaq, Ayah 1

And from his narration on the authority of Ibn 'Abbas that he said in the interpretation of Allah's saying (O Prophet!): '(O Prophet!) And this includes his community. (When ye (men) put away women) He says: tell your people, when you want to divorce women, (put them away for their (legal) period) divorce them when they become pure from their menses and they have not had sexual intercourse with them (and reckon the period) reckon their periods of purity following three periods of menstruation which are followed by major ritual ablution which, for this denotes the end of the waiting period (and keep your duty to Allah) and fear Allah, (your Lord) and do not divorce them when they are not ritually pure, as this goes against the prophetic practice. (Expel them not from their houses) where the divorce has taken place until the waiting period is over (nor let them go forth) until the elapse of the waiting period (unless they commit open immorality) unless they commit an evident sin, i.e. going out during the waiting period without her husbands' permission. Thus, expelling them from their homes during the waiting period is a sin and their going out in their waiting period is also a sin; it is also said that (unless they commit open immorality) means: unless they commit an act of adultery witnessed by four people, in which case they should be stoned. (Such are the limits (imposed by) Allah) these are the legal rulings and obligations of Allah about women regarding expenditure and lodgement; (and whoso transgresseth Allah's limits) and whoever transgresses Allah's legal rulings and obligations and that which He has commanded regarding expenditure and lodgement, (he verily wrongeth his soul) he harms his own person. (Thou knowest not) i.e. the husband does not know: (it may be that Allah will afterward) after the first pronouncement of divorce and before the end of the waiting period (bring some new thing to pass) i.e. love between the husband and wife and return to each other.