Wife to ISIS: Hostage Alan Henning was helping Muslims, so why kill him?

Dr. Shameela Islam-Zulfiqar shared images with CNN from the December 2013 aid convoy to Syria she made with Alan Henning, who was kidnapped from the group. Henning, a taxi driver from near Manchester, England, was part of a team of volunteers that traveling to Syria to deliver food and water. He was abducted from the convoy the day after Christmas by masked gunmen, according to other members of the convoy. Here, Henning stands alongside one of the ambulances he was driving as part of the convoy. The photo was taken close to the Turkish border during a break in the road trip.

(CNN) -- The wife of Alan Henning -- a British aid worker whose life has been threatened by ISIS -- pleaded Tuesday with his ISIS captors to release him, saying he'd gone to Syria to 'help his Muslim friends' and doesn't deserve to die.

In a message released by the British government, Barbara Henning said that she'd just heard an audio file of her husband 'pleading for his life' but hasn't been able to contact those holding him.

'Islamic State continue to ignore our pleas to open dialogue,' she said.

So -- without the chance to talk to his captors directly -- Barbara Henning instead made made another public pitch for her husband's life. A taxi driver from near Manchester, England, Alan Henning 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.

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Barbara Henning noted the widespread sentiment voiced by Muslim leaders around the world calling for Alan's release.

'I have seen Muslims across the globe question Islamic State over Alan's fate,' she said. 'The voices of the people have spoken out loud and clear.'

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Similar to what she'd said in a message Saturday, Barbara Henning said that Alan had gone to the region -- not to join one side or the other, or to spy for a certain group -- to do what he could to improve the lives of people in the region.

'He was working with Muslims to help the most vulnerable within Syria. Nothing has changed,' she said. 'He went to Syria to help his Muslim friends deliver much needed aid.'

Henning's friends plead with ISIS to let him go

Barbara Henning said she'd been told that a Sharia -- or Islamic law -- court had found Alan Henning 'innocent of being a spy and declared (him) to be no threat.' Why, then, would ISIS not 'abide by the decisions of their own justice system?' she asked.

'We are at a loss why those leading Islamic State cannot open their hearts and minds to the facts surrounding Alan's imprisonment and why they continue to threaten his life,' she said. 'Please release Alan.'

Wife of captive Alan Henning begs ISIS to let him go