Is it obligatory for a husband and wife to perform ghusl (ritual purification) from janabah (state of ritual impurity following sexual intercourse) if the call to Asr prayer is made and they have not yet satisfied their needs?

It is not obligatory for them to cease intercourse upon hearing the adhan, nor for the sake of catching the congregational prayer. They may complete intercourse, then perform ghusl, and pray, so long as they do not fear the expiration of the prayer's time. If they do fear the expiration of the time, then it becomes obligatory to cease intercourse in order to pray within the allotted time, according to the majority of scholars. Ghusl becomes obligatory upon the insertion of the glans of the penis into the vagina, even if ejaculation does not occur.