What is the ruling on a woman marrying another man before the expiration of her waiting period (iddah) from her first husband, and what is the ruling on her returning to her first husband based on what he heard that she is still considered his wife?

The marriage of a woman during her iddah (waiting period) is invalid. If the woman and the second husband are separated due to the فاسد (irregular/invalid) marriage, she must observe two iddahs: the remainder of her first husband's iddah, and a second iddah from her invalid marriage. Scholars have differed regarding the overlapping of these two iddahs:

- Hanafi school: The two iddahs overlap, and she observes the iddah from the moment of separation, with the remainder of the first iddah being included in the second.

- Shafi'i and Hanbali schools: The two iddahs do not overlap. She observes the iddah for the first husband first, then for the second, except in the case of pregnancy.

- Maliki school: She observes the remainder of her iddah from the first husband, then from the second. It is also said that she observes the iddah from the second and it suffices for both. If she is pregnant, childbirth unanimously suffices for both iddahs.

Based on this, the woman is still in the iddah of her first husband. He may revoke the divorce and take her back if the divorce was revocable (raj'i), or renew the marriage contract with her if it was irrevocable (ba'in). Upon revocation or renewal, his iddah ceases, and the iddah of شبهة (shubhah - doubt/irregularity) begins.