What is the ruling on one who contracts a marriage with a woman whose waiting period (iddah) has not ended, and is she perpetually forbidden to him, and who among the Companions and jurists held this opinion?

Marrying a woman observing her iddah (waiting period) is forbidden by consensus, based on the Almighty's saying: "And do not determine to consummate the marriage contract until the waiting period has reached its end." The iddah is for ascertaining the purity of the womb.

So, if he marries her, their marriage is void, and they must be separated. If he has not consummated the marriage with her, some say she becomes permanently forbidden to him. Scholars differed if he has consummated the marriage with her: some say she becomes permanently forbidden to him, and this is the view of Malik, Al-Shafi'i in his old opinion, and Ahmad in one narration. Others say she does not become permanently forbidden to him, and this is the view of the Hanafis, Al-Shafi'i in his new opinion, and a narration from Ahmad, which is the more preponderant view.