Explanation:

The ahasan talaaq: consists of a single pronouncement of divorce made in the period of tuhr (purity, between two menstruations), or at any time, if the wife is free from menstruation, followed by abstinence from sexual intercourse during the period if iddat. The requirement that the pronouncement be made during a period of tuhr applies only to oral divorce and does not apply to talaaq in writing. Similarly, this requirement is not applicable when the wife has passed the age of menstruation or the parties have been away from each other for a long time, or when the marriage has not been consummated. The advantage of this form is that divorce can revoked at any time before the completion of the period of iddat, thus hasty, thoughtless divorce can be prevented. The revocation may effected expressly or impliedly.

Thus, if before the completion of iddat, the husband resumes cohabitation with his wife or says I have retained thee" the divorce is revoked. Resumption of sexual intercourse before the completion of period of iddat also results in the revocation of divorce.