al-'iilaa'

al-'iilaa' In the Pre-Islamic Period of Ignorance when a man did not love his wife and did not want her to marry anyone else, he would take an oath to never touch her or to not touch her for a year or two years intending to harm her by means of doing so. Thus, he left her hanging. Neither was she a wife nor divorced. Allaah intended to place a limit on this so He stipulated four months and made void that which was beyond it to prevent any harm [to the woman].

Allaah says in the Qur'aan: For those who swear not to have sexual relations with their wives is a waiting time of four months, but if they return [to normal relations] - then indeed, Allah is Forgiving and Merciful.

[Qur'aan 2:226]

كان الرجل في الجاهلية إذا كان لا يحب امرأته ولا يريد أن يتزوج بها غيره يحلف أن لا يمس امرأته أبداً أو السنة والسنتين بقصد الإضرار بها، فيتركها معلقة لا هي زوجة ولا هي مطلقة فأراد الله عز وجل أن يضع حداً لهذا الجور، فحدده بأربعة أشهر وأبطل ما فوقها دفعاً للضرر

Reference(s):

The Juristic Encyclopedia of Fiqh Volume 3 Page 126