- Group calls on UK government to negotiate for Alan Henning's release
- Henning was kidnapped in Syria as he was helping an aid convoy
- His wife says ISIS hasn't responded to her attempts to communicate
- Leading Muslims in the UK say killing Henning isn't permitted by Islamic law
The wife of British hostage Alan Henning pleaded Saturday with ISIS to release him, describing her husband as a "peaceful, selfless man" who was only in Syria to help people in need.
"I cannot see how it could assist any state's cause to allow the world to see a man like Alan dying," Barbara Henning said, according to a message released by the UK Foreign Office. ISIS refers to itself as "the Islamic State."
Alan Henning, a taxi driver from near Manchester, England, was part of a team of volunteers that traveled to Syria in December to deliver food and water to people affected by the Middle Eastern country's devastating civil war.
He was abducted the day after Christmas by masked gunmen, according to other people in the aid convoy.
In a videotaped execution of British aid worker David Haines, made public last weekend, ISIS displayed Henning and threatened to kill him next.
No response to messages
The Sunni extremist group, which controls large areas of Iraq and Syria, has already beheaded three Western captives in recent weeks -- Haines, and the American journalists James Foley and Steven Sotloff.
The videos of the executions have pointed to U.S. airstrikes against ISIS forces in Iraq as the motivation. In Haines' case, the militant group described the killing as "a message to the allies of America."
Henning's wife said her husband, a father of two, was only trying to do good in Syria.
"Alan is a peaceful, selfless man who left his family and his job as a taxi driver in the UK to drive in a convoy all the way to Syria with his Muslim colleagues and friends to help those most in need," she said in the statement.
She expressed concern that his captors weren't answering her calls for his release.
"I have sent some really important messages but they have not been responded to," she said.
'Executing this man is not the answer'
ISIS has shown no regard in recent weeks for pleas from the families of its Western hostages.
Days before Foley's killing was made public on August 19, his family sent the extremists a message, asking them to show mercy. But they never heard back.
The week before Sotloff's execution became known, his mother released a video pleading with ISIS leader Abu Bakr al-Baghdadi not to kill him.
And news of Haines' death came the same day that his family released a brief message to his captors through the UK Foreign Office.
Henning's wife urged the militants to respond.
"I pray that the people holding Alan respond to my messages and contact me before it is too late," she said. "When they hear this message, I implore the people of the Islamic State to see it in their hearts to release my husband, Alan Henning."
Leading Muslim figures in the United Kingdom have also called for Henning's release in a video posted on YouTube in which they say that killing him isn't permitted by Islamic law.
"Whatever your grievance with American or British foreign policy, executing this man is not the answer," said Shaykh Haitham Al Haddad, a judge on the Shariah Council in London. "We ask you to adhere to the Shariah ruling on this matter and release him immediately and unconditionally."
The only non-Muslim
Henning was making his fourth trip to Syria with an aid convoy when he was abducted.
While part of the convoy stopped at the Turkish border, Henning -- the only non-Muslim in the group -- volunteered to cross into Syria with a 10-person advance party.
In video shot on that day, he explained part of his rationale for answering the call to help. "It's all worthwhile when you see what is needed actually gets where it needs to go," he said, before hugging a colleague.
Henning was kidnapped the next day.
Dr. Shameela Islam-Zulfiqar, a volunteer doctor who stayed behind the main part of the convoy at the Turkish border, said they got a phone call saying Henning had been taken by masked gunmen.
"This was something that we thought was just a temporary measure, with him being a non-Muslim and being visibly English," she told CNN.
The other members of the convoy thought "that they would just question him further and then they would let him go," she said. But amid clashes between ISIS and rival rebel factions in the area, that didn't happen.
'He is not to blame'
Now, Islam-Zulfiqar says she has a message for the people holding Henning.
"As your sister in Islam, I would implore you and beg of you: please spare the life of this innocent man," she said. "He is not part of your struggle. He is not to blame for the actions of Western governments that you fight."
CAGE, a Muslim-led human rights advocacy group in London, also called for Henning's immediate release, saying he wasn't involved in any hostilities toward Muslims.
But in a marked difference from other groups issuing appeals, CAGE called on the UK government to negotiate with the hostage takers.
Asim Qureshi, research director of CAGE, told CNN on Sunday that the releases of Turkish and continental European hostages through negotiations "should act as a wake-up call to the British government."
He's called 'Gadget'
Islam-Zulfiqar said other members of the convoy gave Henning the affectionate nickname "Gadget," for his love of all things technical.
"He really is the guy that fixes everything," she told CNN.
In Henning's hard-scrabble hometown of Eccles in northern England, well-wishers have tied yellow ribbons to lampposts and street signs. None of his workmates at the taxi company nor any of the neighbors on his street were willing to talk to the news media.
Islam-Zulfiqar says the situation is really difficult: "We know time is running out."
Asked how people should think of Henning in his hour of need, she mentioned his smile, his concern for those around him and "his beautiful, beautiful golden heart."