Reference: Fataawa az-Zawaaj wa ‘Ishratun-Nisaa. – Question 72, Page 103
Question: Does the woman fall into sin if she refuses her husband when he calls her [to his bed] if she is suffering from a fleeting mental lapse, or she is ill and suffering from pain?
Response: It is obligatory upon the woman to respond to her husband if he calls her to his bed. However, if she is ill due to a mental lapse and is unable to face her husband, then in this situation it is not permissible for her husband to request her [to satisfy his [sexual] needs] as the Prophet (sal-Allaahu ‘alayhi wa sallam) said:
«There is to be no harm and no causing of harm».
And it is upon him to restrain himself and seek to satisfy [himself] with his wife in a manner which will not cause any harm [to her].