After divorce, is it necessary for a woman to observe the Iddah, even if there has never been any physical relationship between the husband and wife?
There are two scenarios to your question:
1) If divorce occurs before consummation of marriage and before the husband and wife were able to be together in privacy (khalwa), then, upon divorce, the woman does not have to observe the waiting period (idda). She is free to re-marry immediately after the divorce. Allah Most High says:
“O you who believe, when you marry believing women and then divorce them before you have touched them, then they have no obligation of any waiting period (idda) for you that you may count…” (Qur’an 33:49)
The words “before you have touched them” in the above verse refers to sexual intercourse; whether actually, or effectively such as foreplay or being in privacy. (See: Ma’arif al-Qur’an 7/179)
2) If divorce occurs after consummation of marriage, or the marriage is not consummated but the couple have been in seclusion, then, upon divorce, the woman will have to observe the waiting period (idda).
The renowned classical Hanafi jurists Imam Haskafi and Imam Ibn Abidin (may Allah have mercy on them) both explain that the cause (sabab) for the obligation of the Idda is marriage being contracted, and then this marriage contract being reinforced by consummation or that which takes the same course as consummation such as death or remaining in privacy, and thereafter, separation (furqa) taking place. (See: Radd al-Muhtar ala al-Durr al-Mukhtar 3/504)
The meaning of “privacy/seclusion (khalwa)” is that the married couple remain alone in a way that sexual intercourse is possible even if there is a Shari’ah-based reason preventing them from having sex (khalwa al-fasida) such as the woman is fasting or she is on her menstrual period. As such, even if the couple did not touch each other but they were together alone even for a short period of time, then upon divorce, the woman will have to observe the Idda. (Ibid)
The above explanation also serves as an answer to the oft-asked question: Is a woman required to observe the Idda in spite of being separated from her husband for a long time? In light of the above, it becomes clear that as long as the couple have been in privacy after marriage, she is obliged to observe it upon divorce even if she had been separated from her husband for many years.
Unfortunately, many Muslims are mistaken in believing that the sole reason for the obligation of the Idda is to ensure that the woman’s womb is clear. Undeniably, this is one of the primary wisdoms but there are many other reasons and wisdoms for the Idda becoming obligatory such as expressing sadness over an unfortunate incident. As such, even if divorce occurs after many years of separation, the woman must observe the Idda, provided she had been in privacy with her husband once since being married.
And Allah knows best
[Mufti] Muhammad ibn Adam
Leicester , UK