Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- The marital relation is a serious matter that requires a careful approach.
2- Having sexual relation with the divorced wife after the iddah (waiting period) is considered adultery which is a grave sin that necessitates sincere repentance. So, you both have to repent to Allah and then you can re-marry again.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you did have sexual relation with your wife after the expiry of iddah, then you are guilty of a major offence; it is adultery.
I advise both of you to seek repentance and beg for Allah’s mercy.
Once you have repented, you may re-marry by going through the standard requirements, since it was the first divorce.
Having said this, I should also advise you never to use words of divorce jestingly.
You may seek marriage counseling and try to reconcile your differences amicably so that you won’t end up repeating the same mistakes again.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.