Barbara Henning, the wife of British hostage Alan Henning, has urged his Islamic State captors to "please release him, we need him back home".
The 47-year-old aid worker was captured by militants in Syria last year and has been threatened with death by his Islamic State captors.
British Muslim scholars have called for the release of a British aid worker being held by Islamic State, describing the threats against him as "totally prohibited" under Islamic law.
Alan Henning, 47 , the former taxi driver from Manchester, was threatened by IS militants at the end of a video showing the murder of David Haines.
In a YouTube video, Shaykh Haitham Al Haddad appeals for the immediate and "unconditional" release of Henning, telling militants: "executing this man is totally harem (prohibited) according to Sharia."
"Whatever your grievances with American or British foreign policy, executing this man is not the answer," Al Haddad added.
Imam Shakeel Begg, of Lewisham Islamic Centre, says there is "no justification in our religion that allows you to continue to hold him let alone harm him".
The video comes after more than 100 Muslim leaders from across the UK signed an open letter calling for Mr Henning's release.
The oldest member of Alan Henning's family has demanded boots on the ground to combat Islamic State militants who killed their beloved Alan.
The wife of a British aid worker held by Islamic State militants has recorded a message to his captors appealing for his life to be spared.