What is the ruling on one who said to his wife: "I swear by divorce that if you leave the country we live in by yourself, I will divorce you," and then she left with her sister, and a month later she left by herself?

The majority of scholars hold that a conditional divorce takes effect if the condition is met. However, Sheikh al-Islam Ibn Taymiyyah is of the view that an expiation for breaking an oath (kaffarat yameen) is required if the husband did not intend divorce but rather threat or prevention.

Based on this, if you swore by divorce to your wife that you would divorce her if she went out alone, then her going out for the first time with her sister does not constitute a breach of the oath. As for her going out alone for the second time, if you fulfill your promise and divorce her, the divorce takes effect. If you do not fulfill it, then divorce also takes effect according to the majority of scholars due to the fulfillment of the condition, contrary to Ibn Taymiyyah's view.

The fatwa (definition) follows the madhhab (definition) of the majority. You can revoke the divorce before her 'iddah (definition) (waiting period) expires if this was a first or second divorce. Her 'iddah ends with her purification from the third menstrual period after the divorce, or after the passage of three months for a non-menstruating woman, or upon giving birth for a pregnant woman. If her 'iddah has expired, then a new marriage contract is required. If this was a third divorce, then she is unlawful for you until she marries another husband in a genuine marriage and he divorces her after consummation.