She apostatized and married a Christian; now she has returned to Islam and has left that Christian man – how long is her ‘iddah?

We
put this question to Shaykh Muhammad ibn Saalih al-‘Uthaymeen, may
Allaah preserve him, who responded by asking:

 “Did
he have intercourse with her?”

 (We
said:), Yes, he had intercourse with her.

 His
response: (Her ‘iddah) is one menstrual cycle – according to the more
correct view. It was also said that she should wait for three menstrual
cycles, but the more correct view is that her ‘iddah is one menstrual
cycle, because her marriage to that Christian was valid at the time when
she was an apostate. And Allaah knows best.