Shaykh Muḥammad ibn Hādī al-Madkhali explains that if the ʾadhān of Fajr is called while a person is having intercourse during Ramadan, it is obligatory to stop immediately. There is no blame upon the person for doing so, and the fast remains valid.
‘What is the ruling on the ʾathān of Fajr being called [in Ramaḍān] whilst he is having intercourse with his wife?’
Meaning the caller to prayer has called the ʾathān and he is having intercourse with his wife. It is obligatory upon him to stop and there is nothing upon him.
