What is the required waiting period for a woman who has committed fornication?
Chapter on What is Prohibited to Marry and Combining Between Them and Other Matters
Al-Mughni
Book of Marriage
Primary text
If the rule regarding pregnancy is established, the woman must observe an Iddah, and marriage is prohibited during it. This is because the original purpose of the Iddah is to ascertain the purity of the womb. Moreover, before the Iddah, there is a possibility she is pregnant, which would invalidate her marriage, similar to a woman impregnated through a misconception (Shubhah). The Iddah of a woman who committed Zina is like the Iddah of a divorced woman because it is a period of purification for a free woman, thus resembling the Iddah for one impregnated through Shubhah.
Supporting text
Ibn Abi Musa narrated that she should be purified by one menstrual cycle, as the act does not stem from a valid marriage or a marriage in error, resembling the purification of an Ummu Walad upon manumission. However, the correct view is that the Iddah should be like that of divorce, because if marriage to a pregnant woman is invalid, marriage to a non-pregnant fornicator is even more strongly prohibited due to the potential confusion of lineage if she conceives from the new husband, and because intercourse in the private part necessitates Iddah, similar to intercourse through Shubhah.