Short Answer
When divorce is pronounced it may be revoked by the husband saying ‘I take you back’ or ‘I revoke the divorce’. This is the recommended method to retract a divorce. He may also revoke the divorce by being intimate with his wife by kissing or caressing her with desire, though that is somewhat disliked [makrūh].
It is also recommended to appoint two official witnesses to avoid potential disputes. If she claims the divorce was not revoked, and he does not have two witnesses, her word will be accepted in court.
If the divorce is not revoked within the waiting period [ʿiddah] it becomes final and the two are no longer husband and wife.
What the Qur’an and Sunnah Say
Allah says, “So, when they [the divorced women] have [almost] reached their term [of iddat], then either retain them with fairness, or part with them with fairness. And make two just men from among you witnesses [of your decision]. And [O witnesses], keep your testimony upright for the sake of Allah.” (Qur’an, At-Talaq 65:2)
“Divorced women shall keep themselves waiting for three periods, and it is not permissible for them to conceal what Allah has created in their wombs – if they believe in Allah and in the Last Day. Their husbands are entitled to take them back in the meantime, if they want reconciliation…” (Qur’an, Al-Baqarah 2:228)
What the Scholars Said
Imam Haskafi said, “It is recommended to notify her [the wife] of the revocation, so that she does not marry someone else after the expiry of the waiting period.” (ad-Durr al-Mukhtar 3:401)
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Shaykh Mustafa Umar