What is the ruling of Sharia concerning a man who swore an oath of divorce upon his wife that she should not go to her sister, then he found her there, bearing in mind that she is now with her family?

The husband's statement to his wife, "You will be divorced if you go to your sister," is a conditional divorce.

The majority of scholars hold that this divorce takes effect if the condition is met (the wife going to her sister).

However, some scholars are of the view that conditional divorce has two scenarios: 1. If the husband intended the divorce to occur, then it counts as one divorce. 2. If his intention was merely to threaten or prevent, then he is obligated to offer an expiation for breaking an oath (kaffarat yamin), and no divorce takes place.

According to the view that the divorce takes effect, one revocable divorce occurs, and the husband may take his wife back before her waiting period ('iddah) expires.