Is it permissible for a husband to take back his wife from an unregistered marriage without her knowledge, and how can divorce be proven if the husband divorces her without her knowledge and claims to have torn up the divorce paper, which was not done in front of witnesses, and the wife fears that the husband will show the paper after she has become engaged to another person?

An unregistered marriage, if it fulfills its pillars and conditions—namely, a guardian, witnesses, and a صيغة (formulation of offer and acceptance)—is valid, even without official documentation. In such a marriage, a husband's resumption of marital relations after a divorce is valid without the wife's knowledge or consent, by scholarly consensus. Divorce occurs simply by the husband uttering it and does not require witnesses, though proving it necessitates two witnesses. If a husband divorces his wife in an unregistered marriage, he can take her back (راجعها) before the expiry of her iddah (definition) (waiting period) without her knowledge. However, after the expiry of the iddah, his claim of resumption will not be accepted unless there is testimony from two just witnesses.