Lillatheena yu'loona min nisa-ihim tarabbusu arbaAAati ashhurin fa-in faoo fa-inna Allaha ghafoorun (surah Baqarah: 226)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(2:226) Those who take an oath to keep apart from their wives are given four months (for a final decision), *245 Then if they resume their relations, Allah is Forgiving and Merciful. *246

Lillazeena yu`loona min nisaaa`ihim tarabbusu arba`ati ashhurin fain faaa`oo fa innal laaha Ghafoorur Raheem

*245). In the legal terminology of Islam this is known as ila'. It is obvious that harmony and cordiality do not always prevail in matrimonial life. There are occasions when strains and tensions develop, leading to discord and estrangement. But the Law of God does not approve of that discord which causes a husband and wife, who are legally tied to one another in matrimony, to remain for all practical purposes alienated from one another as if they had ceased to be spouses. For this kind of abnormal discord and estrangement God has fixed a limit of four months during which the spouses are required either to settle their difference, or to break the tie of wedlock so that each becomes free to contract marriage with someone with whom a harmonious matrimonial relationship appears more likely.
Since the verse mentions 'taking a vow', the Hanafi and Shafi'i jurists consider the injunction to be applicable only when a husband has taken a vow not to have sexual relations with his wife. According to them, the injunction does not apply if the husband merely forsakes sexual relations with his wife without taking any vow to that effect. The Maliki jurists are, however, of the opinion that irrespective of whether a person has taken a vow, the maximum permissible limit for abstaining from sexual relations in wedlock is four months. A statement to that effect is also attributed to Ahmad b. Hanbal. (See Ibn Rushd, Bidayat al-Mujtahid, vol. 2, pp. 98 ff. - Ed.)
According to 'Ali, Ibn Abbas and Hasan al-Basri, this injunction is related to the cessation of sexual relations as a result of unpleasantness in the relationship of the spouses. It would not apply, however, if a husband were to decide to abandon sexual relations with his wife out of some beneficial consideration - say because the wife is breastfeeding - at a time when their relationship was pleasant. According to other jurists, however, any vow which prevents sexual intercourse between a husband and wife is ila', and ought not to last longer than four months irrespective of the state of the matrimonial relationship when it was taken. (See Jassas, Ahkam al-Qur'an, vol. 1, pp. 355 ff - Ed.)
*246). Some jurists have interpreted this verse to signify that if the spouses break their vow and re-establish sexual relations they will not be liable to any expiation and will be pardoned by God gratuitously. However, the majority of jurists are of the opinion that they, are required to expiate. The statement that God is Oft-Forgiving and Merciful does not mean that God has forgiven them. It means rather that God will accept their expiation and will forgive them for whatever excesses they may have committed against each other.