The family of a murdered American Christian aid worker received the Presidential Medal of Freedom in a ceremony at the White House on Tuesday.

Dr. Tom Little and other members of his medical team were killed by the Taliban in Afghanistan last summer. He had worked as an optometrist there for more than 30 years.

President Obama presented the medal to Little's wife, Libby.

The president said Dr. Little "was guided by his faith, and he set out to heal the poorest of the poor in Afghanistan."

He said Little lived the lesson of New Testament scripture found in John 15:2-13 that reads, 'Greater love hath no man than this, that a man lay down his life for his friends."

The Presidential Medal of Freedom is presented by the president of the U.S. and along with the equivalent Congressional Gold Medal, which is awarded by an act of the U.S. Congress, is the highest civilian award in the U.S.