What is the ruling on a woman who marries after the expiration of her waiting period (iddah) following her husband's death, and then this husband reappears?

If the missing person returns: If the second husband had not consummated the marriage with the wife, she is returned to the first husband immediately, and her marriage to the second husband has no effect. But if he had consummated the marriage with her, the first husband has the choice between having her returned to him, and he must abstain from her until her waiting period (iddah) from the second husband concludes, or allowing her to remain with the second husband, and the first husband then claims her dowry (sadaq) from the second husband. The Companions (may Allah be pleased with them) ruled accordingly.